Darth Omar
Russian asset
Do do we pick areas to ban by throwing darts on a map?
No lol.
It comes down to probabilities: any region with a high Muslim population is going to have X amount of radicals.
There's also a logical issue at work. Just because no refugees have gone jihadist, yet, it doesn't follow that they never will. In fact, using probabilities, if you let a hundred thousand in you can pretty well bet the farm you are letting some jihadists in.