Another interesting side effect of Muslim extremism is that it dends to de-assimilate moderate Muslims and absorb them. Moderate Muslims in Europe tend to fall under the orbit of extremists once they start gaining enough gravity. This is reflected in an increase in radicalization of second and even third generation immigrants.
Granted, European countries often exacerbate this problem by failing to thoroughly assimilate their immigrants in the first place. The isolated North African ghettos of Paris are the perfect incubators for radical Wahabbism, even if they are mostly moderate now. Muslim Europeans that are treated like strangers in their own country will be easy prey for would be Abu Musab al Zarqawis with dreams of insurgency and revolution.
"Granted, European countries often exacerbate this problem by failing to thoroughly assimilate their immigrants in the first place. The isolated North African ghettos of Paris are the perfect incubators for radical Wahabbism, even if they are mostly moderate now."
This is what progressives mean when they say don't promote foreign policy that will provote muslims. In this calculus, so called moderate muslim "yutes" will only embrace radical Islam when they have been sufficiently threatened and offended; they have no free will to take Western response in context, and thus they cannot be held responsible for becoming extreme.