But if it did, then simple reality dictates that either V1 was wrong, or the pope is not a heretic
I agree these are the only two alternatives, but the first is impossible because Vatican I was an Ecuмenical Council and is Dogma.
Therefore, the second must be true: Some passages in Vatican I that exegete and interpret the Lord's Promise of never-failing Faith.
[...]
Do we think Vatican I's explanation of the Lord's Promise to St. Peter can be mistaken? I cannot see how that could be the case.
The second is most assuredly as wrong as the first point Xavier. All one needs to do is know of anything that any of the conciliar popes have said or written to know they speak heresy.
What is now needed, is to examine both of the indisputable facts and form an indisputable conclusion, based on those facts:
1) V1 is right.
2) The pope preaches heresy.
This only means your understanding of what V1 taught, is wrong.