Islam can be a particularly grim religion. Wahhabism is a truly hideous sect of it, for example, one that openly advocates 'smiting the infidel' and so on, and there are others. There is something about it that can be taken to encourage a fundamentalism that few other religions match. It's not necessarily that the Koran (and the other holy books of the Islamic faith) are particularly intolerant compared to others - the Bible has numerous bits and bobs that would happily sit in some of the Koran's worst passages. As does it's predecessor, the Torah.
The latter bears even more similarity as it also shares the strict life code that the Koran does (the Bible is less so in this respect, despite the Old Testament basically being the Torah, the New Testament defines Christianity rather more and it is fairly lax in it's life 'code'), but only seems to serve, at it's fundamental end, to encourage a fairly happily isolated and imbued with a sense of superiority/near arrogance population that seems to live by the tenant 'We're right... but do what you want, so long as you leave us alone'. Fundamental Christianity serves as more of a ignorant nusiance, intellectually harmful but otherwise fairly toothless.
And most of the Eastern religions largely don't give a **** and just get on with it.
The Abrahamic religions lend themselves to politics more openly, I think, and in the case of fundamental Islam, it becomes dangerous.
I don't like any religion, as the forum will be well aware, and while Christianity gets most of my ire, I have an immense disdain for Islam too. Of course most Muslims aren't really all that different to your average Christian.