If X doesn't offend you, why would self-modify to make X offend you to stop people from doing X, since X doesn't offend you?

Status games. There's a satirical blog which addresses this, at least in the context of Western sophisticates:

....the threshold for being offended is a very important tool for judging and ranking white people. Missing an opportunity to be outraged is like missing a reference to Derrida-it’s social death.

ETA: In the context of Islamic reaction to the Mohammed cartoons as well as the burning of a Koran, there may be some value for a demogogue to conjure up atrocities by some demonized enemy in order to unite his (and in this case, it will be "his") followers. Westerners have done the same sorts of things as well, most obviously in wartime propaganda.