I have my issues with Sedevacantism, but not when it comes to rejection of the false popes of the Conciliar Church. Once a pope espouses and teaches a heresy, he ceases to be pope de jure; he remains in the seat until removed; that's simply a fact, of course (he's sitting there). But his authority is gone, and he has no claim to obedience. He becomes anathema by virtue of his denial of the "doctrine of Christ" and promotion of an "anti-gospel."
Not a fact, rather that's actually a theological opinion and nothing more.
The question was also raised by a Cardinal, “What is to be done with the Pope if he becomes a heretic?” It was answered that there has never been such a case; the Council of Bishops could depose him for heresy, for from the moment he becomes a heretic he is not the head or even a member of the Church. The Church would not be, for a moment, obliged to listen to him when he begins to teach a doctrine the Church knows to be a false doctrine, and he would cease to be Pope, being deposed by God Himself....
....If that quote is accurate as to a discussion at Vatican I, it pretty much says it all.
"What is to be done with the Pope if he becomes a heretic?” It was answered that..."
It was answered.....by whom?
Vatican One states that:
"they stray from the genuine path of truth who maintain that it is lawful to appeal from the judgments of the Roman pontiffs to an ecuмenical council as if this were an authority superior to the Roman pontiff."Which is to say no one or no council can judge the pope, not even judge the pope to be a heretic, let alone depose him - V1 states the above quoted opinion is wrong because it "
strays from the genuine path of truth...." Does it not?
Again, aside from disunity, what does sedeism actually accomplish?