Yeah, I don't either.
Yes, rioting isn't free speech. Unfortunately, nothing short of rioting seems to work---the people in question are poor and already at the bottom of the social pile, so their options seem limited.
Democrats already had the African American vote and the cities. Rioting will swing the suburbs back to Republicans, completing the cycle again.
This all will not end well.
P.s. Were there significant riots with the Occupy thing? I seem to recall it being mostly quiet (and completely ineffectual).