I have said this before in this blog site and in my newspaper columns; I am more afraid of domestic terrorists than the Taliban or ISIS.
[inkandvoice.com]
I agree, festering (promoted) hate, can destroy!
Agreed. Not so much because of numbers, though that is an important element. More because of ease of detection. Foreign terrorists must pass through several filters, allowing for earlier knowledge of activity. The homegrown variety, unless incredibly inept, have few if any barriers (particularly true in the case of firearms), and they know the territory.