The trending hashtag.
Frankly, I think these are Twitter idiots who don't represent much of anything that real people are actually even thinking of trying to do. It's Saturday night, and the country is swamped with drunks. And a lot of the tweets with that hashtag are using it to say that it's stupid/evil.
Note: No one is rioting. I heard predictions that there would be riots, and I always thought these predictions were unseemly (if not actively racist). After the verdict was announced, CNN had a reporter in the crowd outside the courthouse, seemingly looking for angry black people to interview — and not finding any.