I'm detecting a distinct war of the worlds vibe here. What exactly is the threat posed by Islam again. Conversion ? - hardly, that only works in quantity when you get them while they are young. So how are they going to impose sharia then.
Fundamentalism is a desperate response to the challenge of consumerism, and perhaps this ties in with the taboo in images of the divine. If it's an image or a symbol it's not real, it stands in for the real, only belief that lives in the heart and mind is, and we are constantly bombarded with images that mean nothing. Perhaps this is why the insult is so grave, I can't tell since I have always had a healthy amount of disgust for religion.