I don't think you are even close on this one. Mel threw a few scenes in on his own, but the story of the passion of Christ comes straight from the Bible. It's nothing new, certainly nothing anyone could have made up.
I would not teach verbatim this movie in a Sunday school, but it did help to get out the reality of what Jesus went through.
"Reality"? Maybe or maybe not.
I finally decided not to see the movie because I do not wish to have The Passion According to Mel—or any other man—stuck in my mind's eye.
The word of God is living and powerful and, as I see it, sufficient for me and mine.