Why not? They did after MLK was killed. I particularly remember that time, because our state Class A (the one with the big schools) basketball tournament was moved from the largest city in the state, and local a little too close to the "hot" zone, to the state capital. We had to play early morning games, games during what were supposed to be breaks between the morning and afternoon sessions and the afternoon and evening sessions of the lower class tournaments. Even our championship game was in such a "time slot". At least I didn't have to go out in the night after being thrown in the shower, fully clothed, after our team won. :).
That is why I go with the sociological approach to what they can do based on what they would do. The ire and primal instincts are to hit close and fast, meaning the neighborhoods in which they are located, only if they are able to do that without resistance would they then branch out (see 3rd world countries as an example) but that wont happen here except in isolated incidents which goes back to my original post about the ...eerr...movement not being monolithic.
Then, (sorry if this is getting long) a lot of the mobs will not be out for "justice, etc." they will be out for looting and mayhem, so it again breaks down the monolithic ability of a riot to last long or wide in a well armed and organized society.
Just my $.02