I have a theory that "radical Islam" is not native Islam, but Westernized Islam. Over half of 75 Muslim terrorists studied by Bergen & Pandey 2005 in the New York Times had gone to a Western college. (Only 9% had attended madrassas.) A very small percentage of all Muslims have received a Western college education. When someone lives all their life in a Muslim country, they're not likely to be hit with the urge to travel abroad and blow something up. But when someone from an Islamic nation goes to Europe for college, and comes back with Enlightenment ideas about reason and seeking logical closure over beliefs, and applies them to the Koran, then you have troubles. They have lost their cultural immunity.

Another relevant fact is that, for most of Islam's history, Islamic nations were militarily equal or superior to anyone that they were likely to come into contact with. Islam was a religion founded by conquerers, not by the conquered, and being in a position of profound weakness compared to Western (Christian/Jewish/secular) civilization is something that's simply never happened to them before. Radical Islam could very well be simply the Islam of the fourteenth century faithfully reproduced in the modern era, and the fact that it tends to involve suicide bombings instead of conquering armies is a matter of circumstance rather than ideology. I suspect that, if the Christianity of the fourteenth century, or the Judaism of the first century, were to be faithfully reproduced today, it would be equally horrifying.