Blasphemy is only offensive to those who believe in the religion. I, personally, don't submit to any religion at all. People takes things way too seriously. Honestly, if you think about it, what's the point of getting all worked up about God, Jesus, the invisible man in your basement, etc.
And neg-repping someone for joking around about something that's really small and insignificant...that's just...a small and insignificant thing to do.