You realize that many of these guys are ISIS? Or muslim brotherhood or anyone of a couple of dozen other mohammedan terror groups.
They are the oppressors.
Yes Some are! However not as many as your think. Most of them are there because of the no questions asked European gravy train. You process them to get them into this “training” you now have control of them and they are not wandering through the countryside. Besides in “processing” them you screen them, ID them as you process them into the camps, any “problems” you deal with immediately. The ID process is particularly important a) The might pop up on a list, b) the now go on a list, c) it intimidates the hell out of them. (They believe movies & TV!). Since you now have them in a “controlled environment” You’re intel service has its best shot at influencing and/or turning some of them.