There are only 2 options to deal with this:
1. SHOOT to Kill All Looters and Rioters immediately, no questions asked
2. Surround the area, make a Perimiter, Round up Every last person involved in the Peaceful Protest when they try to leave and send them to Mexico, far down south
I was thinking along similar lines.
I am guessing that these Terrorist work in a Flash Mob strategy.
All you would have to do is get on their Group Text Message list and then re-send that message to your own group.
Your group would descend on the same location and drive them away.