I'm struggling to see the equivalency here. In one case you have cops, getting paid to protect people and property and ignoring that responsibility (or actually participating in mayhem) at no cost to themselves. Lots of incentive to act poorly, little personal consequence.
On the other hand you have protestors who might collectively benefit from police using force at the cost of taking a club to the head or pepper spray to the face.
Not seeing how the two are comparable.