By "we" here I infer you're not including the "protestants of the dispensationalist stripe" in your previous post.
Which others would you include in the "we?" Calvinists, Arminians, for example?
If they disagree on what scripture supports, wouldn't one or the other have to contradict ("or at best [be] unsupported by) scripture?
Perhaps. It does remind me of the time when I was a new Christian and attended a Bible study with some friends. One of the participants was commenting on some text and reading from the Bible in his hand. I could not find the verse he was reading in the version I was using, so I turned to the person next to me for help. I turned out the person was actually reading from the notes in his Scofield Bible as if they were the very Word of God.
Some men's popes don't live in Rome, but down the street in their local church, or on the radio dial, on in their libraries.
If they disagree on what scripture supports, wouldn't one or the other have to contradict ("or at best [be] unsupported by) scripture?
Absolutely. As they say, if we disagree on a text we can't both be right, but we can certainly both be wrong. Popes, bishops, pastors, teachers, reformers, churchmen of all types suffer from the same affliction. It's called imperfection. If we were omniscient we would be God.