For my very limited money, the real issue isn't whether or not a particular man wearing a white cassock is legit. The real issue is that the society of which the man in white is unquestionably the head is a complete fraud, a counterfeit of Holy Mother Church, devouring its own members and endeavoring to eradicate supernatural faith from this world. We don't just keep our distance from one man, but from the entire, clearly-problematic society/institution/etc. The fact that we refer to it as the Conciliar Church indicates it is an illegitimate invader -- something not limited to just the one man or his predecessors. While the lack of any sort of juridical acknowledgement of this reality is a presently-insurmountable obstacle, we all know that thing headquartered in Rome is not Holy Mother Church and is to be avoided at all costs.
Just as Jesus Christ truly died, why do we think it is impossible that His Mystical Body could die a mystical death, if you will? If you argue that such a thing simply cannot ever happen, how is what has clearly already occurred substantially different?