It is necessary to know who the first pope is. By Divine and Catholic Faith, we believe that St. Peter was the first of many men chosen by Christ to represent Him on earth after His resurrection and ascension into heaven. This, of course is important, so that we may see how the papacy began, and how it developed under the protection of God the Holy Ghost.
It is also necessary to know who the current, or at least the most recent pope is. Without knowing who the current or most recent pope is, then we do not have a authoritative voice to follow, guiding us in matters Divinely revealed.
By recognizing who is an antipope and who is a true pope, we can determine whose teachings we must obey, and those whose teachings we must reject as non-Catholic. Any person who acknowledges as a public or manifest heretic as Catholic, especially one who claims to be a pope, cannot themselves remain Catholic, being in heresy themselves. They are heretical for denying the dogma that heretics, by Divine Law and without the need for any declaration at all, are ejected from the Catholic Church, and out of the way of salvation.
Ignorance itself will not excuse a person from the guilt of infidelity to the true religion, such as subjecting oneself to a heretical antipope, but invincible ignorance alone. Notice also that the following teaching of Pius IX does not state that such persons will be exonerated from the guilt of original sin or other sins against morality. Pope Pius IX never taught that a person in the state of invincible ignorance of the true Faith could be saved, but that there just punishment would not include punishment for infidelity.Pope Pius IX, Singulari Quadem, December 9, 1854:
"For it must be held by faith that outside the Apostolic Roman Church, no one can be saved; that this is the only ark of salvation; that he who shall not have entered therein will perish in the flood; but, on the other hand, it is necessary to hold for certain that they who labor in ignorance of the true religion, if this ignorance is invincible, are not stained by any guilt in this matter in the eyes of God."
It is a definite stretch to assert that a person with the use of reason who has access to other people, books and libraries could be invincibly ignorant of any human knowledge at all. For this reason, and the fact that all human beings have an obligation to find and profess the true Faith of Jesus Christ, in the world today it would be imprudent to attempt to exonerate anyone at all with the excuse of invincible ignorance.
So anyone at all who is subject to a manifestly heretical papal claimant, recognizing them as a Catholic pope, is guilty of infidelity against the true religion. Sadly our recent history is filled with all sorts of such people, including Padre Pio, Sr. Lucia, Malachi Martin and anyone else who submitted to the antipopes of the 20th century, starting with Benedict XV
.St. Mark 13:5-7:
"And Jesus answering, began to say to them, Take heed lest any man deceive you. For many shall come in my name, saying, I am he; and they shall deceive many. And when you shall hear of wars and rumours of wars, fear ye not. For such things must needs be, but the end is not yet."St. Matthew 24:21-25:
"For there shall be then great tribulation, such as hath not been from the beginning of the world until now, neither shall be. And unless those days had been shortened, no flesh should be saved: but for the sake of the elect those days shall be shortened. Then 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 shew great signs and wonders, insomuch as to deceive (if possible) even the elect. Behold I have told it to you, beforehand."
Unless those days had been shortened no flesh should be saved. We should not be surprised to think that most people in the past century have gone to hell for being in schism from the true Faith. Some might here ask: "How could God allow so many people to be cast out of the Church, just like that?"Apocalypse 3:16:
"But because thou art lukewarm, and neither cold, not hot, I will begin to vomit thee out of my mouth."
Needless to say, those who are hot with the love of God know His Faith well enough to spot heresy and to anathematize all heretics, especially those who claim to be the supreme pastor over the whole Catholic Church.