1 Ophelia: Martian invasion?! What?!
1 Mercutio: It's on Slashdot. It must be true.
2 Mercutio: Never-ending ethnic conflicts, global warming, now this. Sometimes I think we should trash the current world, reboot, and restore from the last save set.
3 Ophelia: And how far back would that set us?
4 Mercutio: Around 30 AD. I hear Jesus saved.

This is entirely a throwaway gag, and not the beginning of a conversion into religious themes.

I used to like the comic B.C. by Johnny Hart. When it was about random cavemen doing weird stuff. As the years passed, I noticed it getting more and more religious with its references. This was a reflection of changes in Hart's life which led him to become more religious and conservative in outlook. And B.C. stopped being funny any more. If only he'd made jokes about religion instead of preaching it.

Ah well. Anyway, I just thought this line was funny. Mercutio is not meant to be a religious character. He is simply being irreverent for the sake of silliness.