Obama clings to his politically correct delusions. This one is particularly important to him. Psychologically it was critical for him to define ISIS as not real Muslims. Otherwise it would have been impossible for him to order white infidel Christian pilots to bomb dark skinned Muslim jihadists however barbaric they may be.
Not Obama alone. George Bush and most of our elites keep pushing the idea that radical Islam does not represent the thinking of main=stream Islam. We were told that the hi-jackers on 9/11 were a members of a tiny sect, a small band of fanatics who had been manipulated by their leaders into undertaking their suicide mission. But the evidence is that millions hold the same views. Even if they do not act upon them.