There is a famous photo of Anjem Choudary, the head of multiple banned organizations calling for imposing Sharia law on the UK whose follower was responsible for the Lee Rigby beheading, getting drunk as a young law student. Friends recall "Andy" smoking pot and taking LSD, sleeping around and partying all the time. Andy was really well integrated, but he still turned back into Anjem.
While the proliferation of segregated Muslim areas, no-go zones in which English, French or Dutch is the foreign language, is a major problem, it is a mistake to think that "integration" solves Islamic terrorism.