I’m not so sure. I lived through (more accurately, “in”) two race riots in Cleveland in the 1960’s. There are two (at least) differences between now and then:
1. It was much harder to travel out of the ghettos (that’s what they were called then) than it is now.
2. There were no cell phones then (”flash mobs” anyone?).
If riots hit the SF Bay Area, maybe BART should lock down as a preventative measure. I wouldn't want trouble taking public transit looking for adventure in other neighborhoods.