A person does not qualify for self defense if they have a role in creating the situation wherein they have to "defend" themselves in the first place. I'm not sure what the exact legal language is but I know it has something to do with whether or not the person in question's predicate behavior can be construed as "reckless."

As you said, his bringing lethal weaponry into an active riot situation was "obviously catastrophically stupid." His doing so recklessly escalated the situation and created a predicate wherein lethal violence was more of a possibility than had he not been there. His being on camera earlier in the night saying he's there to defend private property should leave him basically fucked as far as claiming self defense goes.

I guess a sympathetic judge could somehow worm around to it still being self defense but that would set a precedent whereby people could just show up to riots with lethal weaponry, openly deputize themselves as "defenders of private property" and extra-judiciously execute those they decide are presenting a threat in an escalated environment they themselves are partially responsible for creating.