Thanks to Jim West for drawing attention to an interesting and well-written article about The Passion of Christ, situating it in Gibson's career and noticing the recurring crucifixion, violence, death, resurrection and martyrdom motifs that occur throughout his films. It's in a journal called The Village Voice:
Jessica Winter, "Mel Gibson's Jesus Christ Pose"
I would have thought that some of this is straightforwardly explained by the suffering / death / resurrection schema that is common to many films, E.T. being a classic example, and some is explained by Gibson's obsession with showing graphic violence, but in spite of that, I think Winter is on to something here.