Well if they handle things like that in that way in Peru, I can't condone that.
And yes there used to be some serious altercations between opposing groups in America but those were usually labor disputes, strike breakers and such. But from the Watts riots and onward, usually the violence has been pretty one sided with the protesters committing most of it.
The few demonstrations I have joined though were organized and managed by people who did not provoke violence, did not allow hateful signs or behavior. We were careful not to interfere with pedestrian or vehicle traffic, did not block entrances to businesses, were pleasant and courteous and not threatening in any way. I will defend that anytime, anywhere.
But I don't care which side is doing it. Those who harm, endanger, threaten or interfere with innocent bystanders going about their lives are wrong and should be subject to penalty of law.