Police needs to start bringing out the riot gear and engaging.
That works until it doesn't work and then what? One of these days the police bringing out the riot gear isn't going to do anything. Most police forces in major cities are a couple thousand. NYC has the largest force and is 40k if these protest spread, there are not enough police, riot gear, nor jails to stop anything.
One day with the way things are going you'll wake up to an America where authoritarian crackdowns in the name of "law and order" don't do anything but get cops hurt and anger boils over until it's uncontrollable.
For once I will actually agree with Grassroots, and violent rioters and looters should indeed be crushed by the police. It is the job of the police to uphold law and order and they are failing miserably.
However the Police should leave peaceful protestors alone.
Of course there comes a point where the police gets overwhelmed, and normally at that point they either call backup or they simply retreat and leave some the rioters alone until they disperse. (probably the ones that are less likely to cause damage and what not).
This video is a good one on explaining how riot control works, though it seems to be centered on the Charlottesville protests: