Consider

At least 129 people were killed as seven gunmen went on a rampage around the French capital -- detonating blasts by the stadium, shooting patrons at restaurants in central Paris and killing dozens at a rock concert. The Islamic State militant group claimed responsibility for the attacks.

Think of it this way.

Seven gunmen.  Untold thousands of emigrees who have tried to flee this kind of nonsense.  

You can alienate the whole to the benefit of the few, or you can welcome the many and isolate the few.

Which is the smarter strategy?