I was reading parts of another thread here which related to Sede Vecantism and was thinking about the position. Is it wrong? No. As long as it remains an opinion, which for most it seems to, it can not be wrong for it is an opinion. But two opinions don't make a right, right? My personal opinion is that I'm blind, or at least naive, to think that these men aren't heretics. But thats an opinion as well.
However, I tend to see much effort put in to the previous 3 and/or 4 popes as an attempt to show why these men could not possibly hold the Seat of Peter. From extensive St. Bellarmine quotations, to archived documents and interviews, etc. But here's what I'm sort of thinking:
If everyone on Cathinfo was magically made a Cardinal today, then I could understand the reason for trying to proclaim wether or not these popes were indeed popes or not, and of course to proclaim all of their heresies. We would have the duty, I believe, to make it known to the world that these men, outside of a last minute conversion from God, were not Catholic, and most definitely did not act as Catholics much of the time.
However, we are not Cardinals. And as such, our only duty is to recognize what is and isn't Catholic and live a holy life attempt to get to Heaven (simplified I know). It is not within our power to proclaim what office these men did or did not hold as I hope future Cardinals will.