From a discussion group:
"if the Pope thought this film (Passion) is accurate, then it certainly parallels the Bible's account of what really happened to Jesus"
Well, we have to trust that the Pope's memory of the Bible is accurate. Then we have to assume Gibson stuck to the Bible, and didn't include those crazy visions of some medieval saint as some reports say.
Also, not everything in the Bible is historically accurate; a lot of it has allegorical and even political purposes. I mean--women were born from a rib? So we have to trust that Gibson stuck to the bible even when it deviates from historical accuracy.
"I wouldn't expect the Pope to claim that the Bible is inaccurate."
He won't, it's his bread and butter. Church dies if people stopped believing in the bible. It's in his interest to approve of this movie.