I'm a Christian myself and I didn't find it offensive. The only thing this flash was making fun of was the reaction to the Passion(well, it did make fun of the ending of the film itself as well). This doesn't seem like a rip off of the South Park episode either.
The voices in this movie were hysterical(I AM THE LEADER OF THE CHRISTIANS! THE WORLD IS OURS ONCE MORE!). The funniest part of this was the ending.
NOW GET ME A COKE, BITCH!