Are you saying that peaceful protests in the US are met with baton-swings to the skull? That seems veritably untrue; there have been a large number of protests recently that have not ended in any violence.
The Dakota Pipeline protestors have been getting maced and tear gassed this past week. There are also reports of protestors being locked in dog cages[1].
That, and the other incidences of protestors using firearms is something anyone managing a protest of this scale cannot control. As long as the leadership involved condemns the gun violence, and the protestors do what they can to stop people from escalating the situation, they cannot be themselves in the wrong.
It is a very common tactic to plant radicals in peaceful protests who will use violence as an attempt to ruin the reputation of the movement, mainly by distraction - "oh, someone shot at the police, they are all violent monstrous scum now, and nobody should listen to their grievances anymore" was used constantly during the occupy protests, and many of those offenders were later found to be plants by either private or even police agencies to break up the protests and destroy their message.
It sure is odd how these evil tools of the Man are never identified and flushed out by the noble, gentle, peaceful protesters before they start committing arson and shooting cops. Nobody noticed that these agents provocateurs were carrying guns? Nobody went up to them while they were getting ready to burn millions of dollars of equipment -- something which requires a lot more effort than just tossing a match -- and said "hey, don't do that, we're all about peace"? The pipeline protesters knew damn well they had bad apples, and they did nothing about it.
[1]: https://www.washingtonpost.com/news/morning-mix/wp/2016/11/0...