This is my favorite kind of blasphemy. Religious types get very unhappy when you make light of their beliefs, but it's a much friendlier way of getting your point across than just stating how flat out wrong you think they are. Also, when you're being at least mildly amusing, people have a harder time siding against you and attacking your statements. Of course, you still have to make valid points, but if you make them in a way that gets a laugh, it's a lot easier to win.

Here's an example.

I don't have much respect for the Biblical version of God. Think about this: When he first creates mankind, he gives them free run of the Garden of Eden. However, he makes a tree, the Tree of Knowledge. He says to the humans, "Hey, you humans! You can be havin' yer fun n' stuff in the Garden of Eden there n' all," (God, in this instance, is from North Dakota,) "but dontcha be eatin' from dat there Tree o' Knowledge, eh, or I'll haveta kick ya outta here, don'tcha know." Then, like some little kid, he waits behind the bush and when their curiosity finally gets the best of them, he jumps out from behind a bush and yells "GOTCHA, eh?" and kicks them out. What an immature bastard God is.
There! Offensive, but not quite mean spirited enough to be downvoted too harshly. Voila!