Is this based on personal familiarity with all the texts involved? There aren't many and they aren't hard to find. Just knowing the texts makes this interpretation of history seem pretty unlikely, or at least simplified to the point of distortion. That being said, it is certainly among the plausible explanations for what occurred.

This is based on Elaine Pagels' research, as I said in my first comment.

The doctrine of the Pope's personal infallibility has not played a major role in the development of Catholic doctrine. According to Catholic doctrine, it almost never applies. I don't want to sidetrack a really interesting discussion... but this seems like a pretty clear factual mistake that might as well be pointed out.

Now that you point it out, I realize I was conflating all instances of papal authority with papal infallibility, which is not accurate.