Regardless of what you and other lefties think about American law it's pretty clear in allowing for people like him to take out guns to defend both themselves and others from violence. He was legally standing around that car dealership to protect it from rioters.
"Take out guns" ... he was 17 and walking around with a rifle looking for trouble, dropped off by his mom from another town. He was hunting.
What I *think* about American law is it's being reframed to enable vigilante justice, in the short term, and civil war in the long term.