I disagree profoundly with Sadiq Khan, I do not mean by that to condemn muslims because some of their members are terrorists. The IRA terorists saw themselves as catholics and 'protecting' their own catholic community.
The problem we need to address, which I mentioned on another thread, is that in our society we have a large number of disaffected and alienated young men, whose origins lie in muslim countries and who have been brought up muslim. These young men fit neither into modern western society, nor into the tradition of tolerant Islamic belief. Most of them are rootless, they move around between countries, have dropped out of education, are jobless, have played with drugs and alcohol, are looking for some purpose in life where they can feel some value.
The discipline and hate of extreme Islamic cults like ISIS seems to them to offer the purpose and value that they are looking for and in a society where they can find no place while they live, the promise of sybaritic pleasures and value in heaven after death has many attractions.
What we need to do is find ways to help these young men find value and stability in their existing communities.