Fanatics end by subverting their own argument. For instance, animal rights activists have some point, and many people feel sympathy with them. But animal rights fanatics do not have a point. They are the sort of people who threaten human beings in their effort to 'defend' animals.

A fanatic commits to an ideal to whatever end. A fanatic throws everything aside to pursue their idea. Take something which it would be good to be committed to, like basic human rights. You might campaign for such a thing. You might spend every day of your life pursuing such a thing. But once you become fanatical about it, anything can happen.

Londoners say, 'We're so proud of our diversity and tolerance,' but what if that diversity ends up making us intolerant?

Rather than being a 'perversion' of Islam, it is truer to say that the version of Islam espoused by ISIS, while undoubtedly the worst possible interpretation of Islam, and for Muslims and non-Muslims everywhere obviously the most destructive version of Islam, is nevertheless a plausible interpretation of Islam.