Yes, actually. It would have stopped this from happening.
What, banning Muslims in the 1980s? This guy was born here a long time ago. We didn't really have these same problems back then. You can't just argue all this stuff in hindsight. I can come up with an infinite number of "solutions" to problems that started decades or even centuries ago.
Further, you can't seriously think banning Muslims would come without consequences, could you? That would damage our relations
(even more) with Muslims for a long time. Banning Muslims now would only encourage more lone wolves who would be appalled by such treatment, on top of all the other issues driving these people.
It's just not that simple!