I agree with extreme vetting for some sources. I'm not sure I agree with the exact method though.
Except there's no vetting that's going to show everything. The scary thing is one can live a mild mannered life and not draw attention to themselves thus passing vetting and then all of a sudden fall off the apple cart.
In my opinion the best way to make things more secure here is for economic growth to happen in the Middle East under a steady rule of law, that way a lot of them have no reason to come here as things are better over there.