'Dom Guéranger, Abbot of the Solesmes Benedictines, said on the matter, “The real Sixth Council, the one to which the Roman Pontiff gave the necessary and canonical form, the one which requires the respect of the faithful, condemned Honorius only as an unfaithful guardian of the deposit of the faith, but not as having himself been an adherent of heresy. Justice and truth forbid us from going beyond that.”

Pope Honorius

The charge against Pope Honorius is a double one: that, when appealed to in the Monothelite controversy, he actually taught the Monothelite heresy in his two letters to Sergius; and that he was condemned as a heretic by the Sixth Ecuмenical Council, the decrees of which were approved by Leo II. But in the first place it is quite clear from the tone and terms of these letters that, so far from intending to give any final, or ex cathedra, decision on the doctrinal question at issue, Honorius merely tried to allay the rising bitterness of the controversy by securing silence. In the next place, taking the letters as they stand, the very most that can be clearly and incontrovertibly deduced from them is, that Honorius was not a profound or acute theologian, and that he allowed himself to be confused and misled by the wily Sergius as to what the issue really was and too readily accepted the latter's misrepresentation of his opponents' position, to the effect that the assertion of two wills in Christ meant two contrary or discordant wills.

Finally, in reference to the condemnation of Honorius as a heretic, it is to be remembered that there is no ecuмenical sentence affirming the fact either that Honorius's letters to Sergius contain heresy, or that they were intended to define the question with which they deal. The sentence passed by the fathers of the council has ecuмenical value only in so far as it was approved by Leo II; but, in approving the condemnation of Honorius, his successor adds the very important qualification that he is condemned, not for the doctrinal reason that he taught heresy, but on the moral ground that he was wanting in the vigilance expected from him in his Apostolic office and thereby allowed a heresy to make headway which he should have crushed in its beginnings.

In the eyes of outsiders it seems like the sedevacantist view could be seen as a desperate attempt to save a defected Church.

How could a Church founded by Christ transform into an anti-church?

And only a few enlightened faithful be able to realize it?

Christ would then have allowed 99.9% of his faithful to be deceived.

It would also set a precedent that at any time Christ's Church could morph into an anti-church in the future.

In addition, it would set a precedent that we can't know if a claimant/ occupant of the chair of Peter is a true pope without each of us privately discerning whether the claimant spoke public heresy.

Antichrist is not a single person, but the hosts of heretics destroying the Church (see St. John Chrysostom, Opus Imperfectum , homily XLIX). 

http://www.ncregister.com/blog/joseph-pronechen/14-major-saints-give-details-about-the-antichrist

Here's just a few quotes from both the bible and saints and popes on the anti-christ.  St Paul speaks of the "man of perdition" and the "lawless one".  The anti-christ is definitely one man.

The supreme religious deception is that of the Antichrist, a pseudo-messianism by which man glorifies himself in place of God and of his Messiah come in the flesh.