Muslim communities around the world, including Europe, want to play the victim role. They want to feel they are the victims. Their land is occupied, their hair cover is being fought by the French, the crazy laws they consider as god's laws are being second guessed, and today law enforcement agents are visiting their sons more often. They want nothing to end this victim mentality. A Muslim rapping against terrorists would do just that.
The history that is taught in Islamic schools is geared towards showing the Ummah as eternal victims of infidels. As a result, a lot of Muslims don't have a clue about the suffering of non-Muslims in the world.
Here's a related post.