I think the Federal troops would know how to handle things of that nature.
Depends on their Rules of Engagement. I don't see Pres. Trump or any general giving permission for lethal engagement even if the Troops are attacked with potentially lethal rocks, bricks, frozen water bottles, etc. It would take live gunfire coming from the commies, and then who do Troops shoot as they meld back into the crowd chaos?
My solution: Position 3-5 snipers around the announced "protest". As it turns into a riot and they start throwing molotov cocktails into the stores, cut them down before they can meld back into the crowd. People live above those stores. Breaking windows and stealing is one thing, attempted murder is another. Time to start the killing of these savages. It would only take a few.