9/11 had Saudi fingerprints all over it
Right. Obviously it took more than a handful of people to plan the attack. However, it only took a few to execute the plan. That's what I'm getting at.
ISIS could easily have a few operatives slip in among the masses of immigrants.
Does that mean that aid should not be rendered? Hell, no.
Does that mean that it would be prudent to carefully screen those seeking aid? Yes, I believe that would be the course of wisdom. (EDIT: damn watchtower vocabulary coming up on me.)
Like I said, a free-for-all of immigration isn't a good idea.