By your logic, assuming that violence justifies counter-violence, the arms upgrades etc. that the police have received in the past could be portrayed as a form of violence. (If not physical, then at least psychological as a form of intimidation or similar) Therefore, the violent reactions are justified, also if they are more violent than past ones.
No, I am not implying "ultimate" justification, but yes, it goes both ways. Look at the comments in this discussion to view evidence of how people are sympathizing with a rioting mob which destroyed or harmed the businesses, property and person of totally innocent third parties.
In the near east there is a similar problem. There is so much violence going on from both sides, that people can sympathize with cruelties from both sides.
