Actually, traditionally, Muslims usually treated the people of the book better than the Jews or the Christians did. The reason, for example, why learned Jewish people started popping up in Muslim Spain in the Middle Ages, was because among the Muslims they didn't suffer the same rampant prosecution that they in Christian lands. It was only with the Muslims' loss in power and cultural significance that they started to become more close minded and fundamentalist. I believe it is basically a desperate way to preserve their culture. Culturally, they feel and they are, effectively under siege.