To address the original question here, “Why are the rioters overwhelmingly white?”
One of the answers is, that ‘the problem of racism’ and of ‘police brutality’ is far far more an assumed perception of white liberals inventing a cause to fight for, far more than it really exists. All these social justice warriors will fight for their created underprivileged masses even if it hurts them.
See these street interviews for example, where the interviewer first speaks to the white libs to hear their [racist] concern for the ‘underprivileged’, and then he speaks to that actual demographic themselves to get their true feelings.