To be fair, the first guy he shot in self defense, based on other footage from throughout the night, seemed angry at the world, shouting racial slurs at anyone and everyone, getting in people's faces, having to be restrained, and just generally being very aggressive.
There were multiple other people there that had full-size rifles also. What if he were 18 rather than 17 at the time? Does that make it OK? Regardless, he was technically legal in carrying the firearm and OC is legal in WI (dumb to me, but is what it is).
I agree that he shouldn't have been there and is a moron, but he wasn't on trial for being a moron.
I agree that it doesn't bode well for future protests/riots, but this case was pretty clear cut, and there very well may be wannabes in the future who try to pull the same defense, but it likely won't turn out well in their favor.