That satan's primary focus is on those who still have the faith, which in one definition, is being subject to the validly elected pontiff.

He doesn't want to disturb the sedevacantists as we see from your post, for he doesn't want to give you any impression that you are in grave error (and de facto enemies of God!):


Dogmas of the Holy Roman Catholic Church

"According to Christ's ordinance, Peter is to have successors in his Primacy over the whole Catholic Church and for all time".


"He left you this sweet key of obedience; for as you know He left His vicar, the Christ, on earth, whom you are all obliged to obey until death, and whoever is outside His obedience is in a state of damnation, as I have already told you in another place."

(God the Father - Dialogues; Treatise on Obedience)


Colossians 2:18-19

"Let no man seduce you, willing in humility, and religion of angels, walking in the things which he hath not seen, in vain puffed up by the sense of his flesh, And not holding the head, from which the whole body, by joints and bands, being supplied with nourishment and compacted, groweth unto the increase of God."

"The devil is not busy in pursuing infidels and such men as live outside the bosom of Holy Church, because he considers them already won."
St. Jerome

GENERAL LAWS OF GOD, FORBIDDING ALL COMMUNICATION
IN RELIGION WITH THOSE OF A FALSE RELIGION

By Bishop George Hay (1729-1811)

Q. What are those laws which prohibit this in general?

A. They are principally these following:

(1) The first is grounded upon the light in which all false religions are considered in the Holy Scripture; for there we are assured that they arise from false teachers, who are called seducers of the people, ravenous wolves, false prophets, who speak perverse things: that they are anti-Christs, and enemies of the cross of Christ; that, departing from the true faith of Christ, they give heed to the spirits of error; that their doctrines are the doctrines of devils, speaking lies; that their ways are pernicious, their heresies damnable, and the like. In consequence of which, this general command of avoiding all communication with them in religion is given by the apostle: "Bear not the yoke together with unbelievers; for what participation hath justice with injustice? or what fellowship hath light with darkness? and what concord hath Christ with Belial? Or what part hath the faithful with the unbelievers? or what agreement hath the temple of God with idols? For ye are the temple of the living God." (2 Cor. 6:14)

Now it is the true religion of Jesus Christ, the true doctrine of His gospel, which is justice and light; all false doctrines are injustice and darkness; it is by our holy faith that we belong to Christ, and are temples of the living God; all false religions flow from the father of lies, and make those who embrace them unbelievers; therefore all participation, all fellowship, all communication with false religions, is here expressly forbidden by the Word of God. We have seen above 2 that we are obliged to love the persons of those who are engaged in false religions, to wish them well, and to do them good; but here we are expressly forbidden all communication in their religion — that is, in their false tenets, and worship. Hence the learned and pious English divines who published at Rheims their translation of the New Testament, in their note upon this passage, say: "Generally, here is forbidden conversation and dealing with unbelievers in prayers, or meetings at their schismatical service, or other divine office whatsoever; which the apostle here uttereth in more particular terms, that Christian people may take the better heed of it."

(2) The next general command to avoid all religious communication with those who are heretics, or have a false religion, is this, — "A man that is a heretic, after the first and second admonition, AVOID; knowing that he that is such a one is subverted, and sinneth, being condemned by his own judgment." (Tit. 3:10)

Here we see another general command to avoid all such — that is, to flee from them, to have no communication with them. But in what are we commanded to flee from them? Not as to their persons, or the necessary communications of society; for then, as the same holy apostle says upon a similar occasion, "You must needs go out of the world." [1] Cor. 5:10) Not as to the offices of Christian charity; for these we are commanded by Christ himself, in the person of the good Samaritan, to give to all mankind, whatever their religion be: therefore, in the most restricted and limited sense which the words can bear, the thing in which we are commanded to avoid them is in all matters of religion; in that in which they themselves are subverted and sin; in things relating to God and His service. In these they err, in these they are subverted, in these they are condemned; therefore in these we must avoid them.

Hence the pious translators of the Rheims New Testament, in their note on this text, say, "Heretics, therefore, must not wonder if we warn all Catholics, by the words of the apostle in this place, to take heed of them, and to shun their preachings, books, and conventicles."

(3) A third general command on this subject is manifestly included in this zealous injunction of the apostle: "We charge you, brethren, in the name of our Lord Jesus Christ, that you withdraw yourselves from every brother walking disorderly, and not according to the tradition which they have received from us." (2 Thes. 3:6)

In this passage, all the different sects of false religions are particularly pointed out; for, however they may differ in other respects they generally agree in this, of rejecting apostolical traditions handed down to us by the Church of Christ; all such the apostle here charges us, in the name of our Lord Jesus Christ, to avoid — to withdraw ourselves from them. Now it is evident that the most limited sense in which this command, so warmly laid on us by the apostle, can be taken, is to withdraw ourselves from them in everything relating to religion, — from their sacraments, prayers, preachings, religious meetings, and the like. It is in these things that they "do not walk according to the tradition received from the apostles". In these things, then, we are here commanded, in the name of Christ Himself, "to withdraw ourselves from them".

Seeing, therefore, that the Holy Ghost, by the mouth of this holy apostle, has so often, and in such strong terms, forbidden all manner of fellowship in religion with those who are out of His holy Church, let us not be deceived by the specious but vain sophistry of cunning men, who lie in wait to deceive; let us not offend our God, by transgressing these His express commands, by joining in the prayers or going to the meetings of such as are separated from His holy Church, lest He should withdraw His holy grace from US, and as we expose ourselves to the danger, leave us to perish in it.

Let us hear and follow the advice and command of the same holy apostle: "As therefore ye have received Jesus Christ the Lord, walk ye in Him; rooted and built up in Him, and confirmed in the faith; as also ye have learned, abounding in Him in thanksgiving. Beware lest any man impose upon you by philosophy and vain deceit according to the tradition of men, according to the rudiments of the world, and not according to Christ." (Col. 2:6) Wherefore, to all those arguments which may be brought from human, worldly, or interested motives, to induce us to join in or to partake of any religious duty with those of a false religion, though in appearance only, we ought to oppose this one, — "God has expressly forbidden it, therefore no human power can make it lawful."

PARTICULAR LAWS OF GOD FORBIDDING ALL COMMUNICATION  
WITH FALSE RELIGIONS, AND ASSIGNING REASONS FOR IT

Q. What are the particular laws on this subject?

A. In the three general commands above mentioned, God Almighty speaks, by the mouth of His holy apostle, as Lord and Master, and lays His orders upon us absolutely. In what follows, He unites the merciful Savior to the Sovereign; and whilst He no less strictly commands us to avoid all religious communication with those who are separated from His holy Faith and Church, He at the same time condescends to engage our obedience, by showing us the strongest reasons for it.

(1) "Beware of false prophets", says our blessed Master, "who come to you in the clothing of sheep, but inwardly they are ravening wolves". (Mat. 7:5) Here Jesus Christ commands His followers to "beware of false prophets" — that is, to flee from them, to be on their guard against them; and He adds this powerful motive, "Lest ye be seduced and ruined by them"; for, whatever appearance of godliness they may put on, though they come to you in the clothing of sheep, yet within they are ravenous wolves, and seek only to slay and to destroy.

To the same purpose He says in another place, "Take heed that no man seduce you; for many will come in My name, saying, I am Christ, and they will seduce many." (Mat. 24:4) "And many false prophets shall arise and seduce many." (ver. 2) Here He foretells the cunning of false teachers, and the danger of being seduced by them, and commands us to take care of ourselves, that such be not our fate.

But how shall we escape from them? He afterwards tells us how: do not believe them, have nothing to do with them, have no communication, with them. "Then", He says, "if any man shall say, to you, Lo, here is Christ, or there, do not believe him. For there shall arise false Christs and false prophets, and shall show great signs and wonders, insomuch as to deceive even the elect. Behold. I have told it you beforehand. If therefore, they shall say to you, Behold he is in the desert, go ye not out; behold he is in the closet, believe it not." (Mat. 24:23)

Can there be a more powerful reason to enforce the observance of His command, or a stronger motive to induce His followers to have no religious communication with such false teachers? Many will be certainly seduced by them; and so will you, if you expose yourself to the danger.

(2) St. Peter, considering the great mercy bestowed upon us by the grace of our vocation to the true faith of Christ, says, that it is our duty to "declare the praises and virtues of Him who hath called us out of darkness into His admirable light". (1 Pet. 2:9) St. Paul also exhorts us to "give thanks to God the Father, who hath made us worthy to be partakers of the lot of the saints in light, who hath delivered us from the power of darkness, and hath translated us into the kingdom of His beloved Son." (Col. 1:12) Where it is manifest that as the true Faith of Jesus Christ is the only light that conducts to salvation, and that it is only in His Kingdom — that is, in His Church — where that heavenly light is to be found, so all false religions are darkness; and that to be separated from the Kingdom of Christ is to be in darkness as to the great affair of eternity. And indeed what greater or more miserable darkness can a soul be in than to be led away by seducing spirits, and "departing from the faith of Christ, give heed to the doctrine of devils". (1 Tim. 4:1) St. Paul, deploring the state of such souls, says that they "have their understandings darkened, being alienated from the life of God, through the ignorance: that is in them, because of the blindness of their hearts". (Eph. 4:18)

On this account the same holy apostle exhorts us in the most pressing manner to take care not to be seduced from the light of our holy Faith by the vain words and seducing speeches of false teachers, by which we would certainly incur the anger of God; and, to prevent so great a misery, He not only exhorts us to walk as children of the light in the practice of all holy virtues, but expressly commands us to avoid all communication in religion with those who walk in the darkness of error. "Let no man deceive you with vain words, for because of these things cometh the anger of God upon the children of unbelief; be ye not, therefore, partakers with them. For ye were theretofore darkness; but now light in the Lord; walk ye as the children of the light,

. . . and have no fellowship with the unfruitful works of darkness". (Eph. 5:6)

Here, then, we have an express command, not only not to partake with the unfruitful works of darkness — that is, not to join in any false religion, or partake of its rites or sacraments — but also, not to have any fellowship with its professors, not to be present at their meetings or sermons, or any other of their religious offices, lest we be deceived by them, and incur the anger of the Almighty, provoke Him to withdraw His assistance from us, and leave us to ourselves, in punishment of our disobedience.

(3) St. Paul, full of zeal for the good of souls, and solicitous to preserve us from all danger of losing our holy Faith, the groundwork of our salvation, renews the same command in his Epistle to the Romans, by way of entreaty, beseeching us to avoid all such communication with those of a false religion. He also shows us by what sign we should discover them, and points out the source of our danger from them: "Now I beseech you, brethren, to mark them who cause dissensions and offenses contrary to the doctrine which you have learned, and to avoid them; for they that are such serve not Our Lord Christ, but their own belly, and by pleasing speeches and good words seduce the hearts of the innocent". (Rom. 16:17)

See here whom we are to avoid — "those that cause dissensions contrary to the ancient doctrine"; all those who, hating, left the true Faith and doctrine which they had learned, and which has been handed down to us from the beginning by the Church of Christ, follow strange doctrines, and make divisions and dissensions in the Christian world. And why are we to avoid them? Because they are not servants of Christ, but slaves to their own belly, whose hearts are placed upon the enjoyments of this world, and who, by "pleasing speeches and good words, seduce the hearts of the innocent" — that is, do not bring good reasons or solid arguments to seduce people to their evil ways, so as to convince the understanding, for that is impossible; but practice upon their hearts and passions, relaxing the laws of the gospel, granting liberties to the inclinations of flesh and blood, laying aside the sacred rules of mortification of the passions and of self-denial, promising worldly wealth, and ease, and honors, and, by pleasing speeches of this kind, seducing the heart, and engaging people to their ways.

(4) The same argument and command the apostle repeats in his epistle to his beloved disciple Timothy, where he gives a sad picture, indeed, of all false teachers, telling us that they put on an outward show of piety the better to deceive, "having an appearance, indeed, of godliness, but denying the power thereof;" then he immediately gives this command: "Now these avoid: for of this sort are they that creep into houses, and lead captive silly women laden with sins, who are led away with divers desires"; and adds this sign by which they may be known, that, not having the true Faith of Christ, and being out of His holy Church — the only sure rule for knowing the truth — they are never settled, but are always altering and changing their opinions, "ever learning, and never attaining to the knowledge of the truth"; because, as he adds, "they resist the truth, being corrupted in their mind, and reprobate concerning the Faith". (2 Tim. 3:5)

Here it is to be observed that, though the apostle says that silly weak people, and especially women, are most apt to be deceived by such false teachers, yet he gives the command of avoiding all communication with them in their evil ways, to all without exception, even to Timothy himself; for the epistle is directed particularly to him, and to him he says, as well as to all others, "Now these avoid", though he was a pastor of the church, and fully instructed by the apostle himself in all the truths of religion; because, besides the danger of seduction, which none can escape who voluntarily expose themselves to it, all such communication is evil in itself, and therefore to be avoided by all, and especially by pastors, whose example would be more prejudicial to others.

(5) Lastly, the beloved disciple St. John renews the same command in the strongest terms, and adds another reason, which regards all without exception, and especially those who are best instructed in their duty: "Look to yourselves", says he, "that ye lose not the things that ye have wrought, but that you may receive a full reward. Whosoever revolteth, and continueth not in the doctrine of Christ, hath not God. He that continueth in the doctrine the same hath both the Father and the Son. If any man come to you and bring not this doctrine, receive him not into your house, nor say to him, God speed you: for he that saith to him, God speed you, communicateth with his wicked works". (2 John, ver. 8)

Here, then, it is manifest, that all fellowship with those who have not the doctrine of Jesus Christ, which is "a communication in their evil works" — that is, in their false tenets, or worship, or in any act of religion — is strictly forbidden, under pain of losing the "things we have wrought, the reward of our labors, the salvation of our souls". And if this holy apostle declares that the very saying God speed to such people is a communication with their wicked works, what would he have said of going to their places of worship, of hearing their sermons, joining in their prayers, or the like?

From this passage the learned translators of the Rheims New Testament, in their note, justly observe, "That, in matters of religion, in praying, hearing their sermons, presence at their service, partaking of their sacraments, and all other communicating with them in spiritual things, it is a great and damnable sin to deal with them." And if this be the case with all in general, how much more with those who are well instructed and better versed in their religion than others? For their doing any of these things must be a much greater crime than in ignorant people, because they know their duty better.

Q. These laws are very clear and strong; but has the Christian church always observed and enforced the observance of them?

A. The spirit of Christ, which dictated the Holy Scriptures, and the spirit which animates and guides the Church of Christ, and teaches her all truth, is the same; and therefore in all ages her conduct on this point has been uniformly the same as what the Holy Scripture teaches. She has constantly forbidden her children to hold any communication, in religious matters, with those who are separated from her communion; and this she has sometimes done under the most severe penalties. In the apostolical canons, which are of very ancient standing, and for the most part handed down from the apostolical age, it is thus decreed: "If any bishop, or priest, or deacon, shall join in prayers with heretics, let him be suspended from Communion". (Can. 44)

Also, "If any clergyman or laic shall go into the ѕуηαgσgυє of the Jєωs, or the meetings of heretics, to join in prayer with them, let him be deposed, and deprived of communion". (Can. 63)

So also, in one of her most respected councils, held in the year 398, at which the great St. Augustine was present, she speaks thus: "None must either pray or sing psalms with heretics; and whosoever shall communicate with those who are cut off from the Communion of the Church, whether clergyman or laic, let him be excommunicated". (Coun. Carth. iv. 72 and 73)

The same is her language in all ages; and in this she shows herself to be the true mother, who will not suffer her children to be divided. She knows her heavenly spouse has declared that "no man can serve two masters; we cannot serve God and Mammon;" and therefore she must either have them to be hers entirely, or she cannot acknowledge them as such. She knows His holy apostle has protested that there can be no "participation, no fellowship, no concord, no pact, no agreement between the faithful and the unbeliever;" and therefore she never can allow any of her faithful children to have any religious communication with those of a false religion and corrupted Faith.

 Footnotes:

1. The Sincere Christian pp. 474 -533, James Duffey and Son, Dublin

2. Ibid.

http://www.catholicapologetics.info

"Catholics, and Sedes are definitely Catholic because they adhere to the Catholic Faith."

Quote from: Capt McQuigg

"Catholics, and Sedes are definitely Catholic because they adhere to the Catholic Faith."

Not only adhering to the Catholic Faith is sufficient. Dogmatically, besides Explicit Faith (cannot be a heretic), there must be a reception of the Sacraments and a submission to the Roman Pontiff (cannot be a schismatic), in order to be a member of the Church.  

Sedes, like protestants, have multiplied into innumerable private sects and home alone phenomenons that have not even agreement among each other.