I fully expect that home-grown extremist Islam is spread through very similar ways as other forms of extremist organizations (like racist organizations). You start by finding individuals who are disaffected and (most likely) lonely; you recruit them by including them in activities and give them a sense of belonging; and over time you radicalize them by feeding them half-truths and outright lies.
The core difference between fundamentalist Islamic organizations and other extremist organizations is that most other extremist organizations are actively shunned by society. If a college or university in the western world had a neo-Nazi organization passing out pamphlets and recruiting on campus they would act immediately and there would be massive outrage throughout the student body and staff; in contrast, in most universities and colleges in the western world with (fairly basic) investigation of some of the clubs and organizations you can find very close ties to fundamentalist Islamic groups.
The problem isn't immigration, the problem is that political correctness doesn’t allow us to prevent the spread of an extremist ideology if it is associated with a protected group.
