None of your long-winded post has anything to do with the passage of mine that you quoted. Most of it is a distortion and taking stuff out of context and misapplying it.
No, the problem isn't with sedevacantists. It's with certain R&R Old Catholic heretics who promote the notion that the legitimate Papal authority can corrupt the Magisterium and the Public worship of the Church. If you hold this, you too are a heretic, and part of the problem, not of the solution, despite your preferences for the smells and bells of the Tridentine Mass.
PS, nor was +Lefebvre Father Sanborn's superior. +Lefebvre had no jurisdiction or authority over anyone.
What an idiot, accusing SVs of schism, when Canon Lawyers clearly state that it's not schismatic to refuse submission to a Pope based on well-founded doubts about his legitimacy. You'll notice that the implied corollary is that it is schismatic to refuse submission WITHOUT doubts about the Pope's legitimacy ... as R&R does. R&R is what's schismatic, and you have the temerity to accuse SVs of it. Your assertion that SVs are separating themselves from the Holy See is begging the question, assuming that Bergoglio and his predecessors are the Holy See. But you claim that it IS the Holy See and you separate yourselves from that See. It's ludicrous that you claim to be united with the Holy See and in submission to it because you pay lip service ("yes, he's the pope") and put up a picture of Bergoglio in the vestibule.
Really, both the stupidity and the bad will involved in this version of the R&R position are almost beyond belief.
And +Lefebvre did not adhere to your errors, despite your assertions, and it's provable from his own words.
There have been sedevacantist groups that have gone into schism. Fr. Chazal lists them, but I can't recall their names just now. And it's not the majority of sedevacantists, but rather a minority that have gone into schism. That's the danger associated with sedevacantism. DR is not saying that all sedevacantists are schismatic. Of course they aren't.
And you tend to go on and on about R&R and a certain belief about the magisterium, but you are the one who quibbles about this. We don't. Archbishop Lefebvre did not address the "corrupt magisterium" problem that you bring up a lot, because it wasn't and isn't necessary. It's only necessary for a sedevacantist to push that view, in order to promote sedevacantism.