It's as simple as people wanting to justify their prejudices. And sets the stage.
(An aside, talking about rape, assault, etc., check out Americans in Afghanistan and Iraq.)
Stories like those also set the stage for more atrocities to be committed against Muslims. God knows there have been a lot, and God knows Westerners don't give a damn. After all, look what they've done to our wimmen. Bastards, all of 'em.