All fundamentalists are simiilar in that they reject the three central concepts of ethics, as the tragic events on 22 July 2011 in Norway made plain once again.
A car-bombed street in Oslo. A government building is destryoed, as is the building housing a newspaper. It was immediately clear that fundamentalists were behind these deeds. The same kind of fundamentalists as those at work on 11 September 2001.
Of course, we were proved right. The perpetrator, a fundamentalist was soon arrested. Except that he wasn't an Islamic fundamentalist, as had been largely assumed, but a Christian fundamentalist. This clearly defined the front line: It was never about Christians against Muslims, but about reason against fundamentalism, regardless of the form that fundamentalism takes.
The danger occurs when someone who completely refuses to think fixates themselves on an 11th century view of the world and ultimately launches their own personal crusade on a holiday island.
Flying airplanes into skyscrapers, a massacre on a holiday island, that is immediately apparent fundamentalism. But there is also the kind of fundamentalism that is currently destroying the USA.
People who are not fixated on the age of the crusades, but on the age of cheap crude oil. Since 1990 alone, crude oil has become 7 times more expensive, while solar power has become 7 times cheaper.
Being a fundamentalist means denying all three central concepts of ethics, as one is firmly convinced that one has found the one and only doctrine of salvation.