Catholic dogma is whatever the pope says it is according to a whole bunch of papal bulls they’ve accepted for centuries.
The Sedevacantists get around this by going through an elaborate logical contortion whereby somehow there is some higher set of Catholic principles and the minute the Pope goes against them he is a heretic and thus the Pope is somehow not really the Pope and the Magisterium that supports him is not really the Magisterium but then they run into the problem of “The Gates of Hell Prevailing Against the Church” they get around this when pressed by saying the Sedes are the righteous remnant but where does there authority to decide all this come from and what is the hidden hierarchy. So no matter they end up de facto Protestants with their own Priesthood of all Sedevacantist believers…
Source: https://blog.jim.com/culture/the-logos-has-risen/#comment-2528698
Comment: In fact, all Sedevacantists have to learn Latin in order to have any skill reading the source texts. Again, hell is eternal.
oogenhand 