This is the kind of more controversial comment Id like to see upvoted to spur good discussion.
The Second Amendment says well regulated militia. Should a group of people be able to organize, with guns, to protect businesses from riots and looters?
This one is looking like a very complicated situation as it unfolds. Someone underage, carrying an illegal gun, probably doesn't fall into well regulated. (Furthermore, what happens if someone underage, carrying an illegal gun, crossed a boarder, is attacked and defends themself? It's food for thought. Is every party, protester, militia, police, simultaneously victim and perpetrator?) That in and of itself doesn't negate the constitutional right of others to do the same thing legally. Just like everything else, a small group of people breaking the law, shouldn't take away everyone elses rights. That goes for rioters not destroying peoples rights to protest. That goes for kids/murderers destroying peoples rights to a militia. If you want to say "protesters arent rioters" thats fine, then protesters and militia shouldnt clash, should both be free to exercise their rights, and if they do, that illegal clash should be prosecuted.
The other comments here are saying "cops should stop..." but that is irrelevant to the fact that it is legal (and the cops were encouraging it at the scene) for people to stand outside a building and protect it. Taking that a step further, and back to the point of the initial article, where does Facebook draw the line in allowing people to self organize to protect their property? Is defensive violence different than offensive violence? And then theres the idea that a militia is designed as a check and balance against an oppressive police/military force. Does suppressing the formation of militia play into the strengthening of unchecked government power?