It’s not a great fit because of two factors the food court patron knew there were others around and saw the YouTuber’s posse standing there with cell phone cameras. If I were on the jury, that would make it less reasonable for the patron to claim he was in fear for his life. He had no reason to assume the YouTuber was armed, and with that evidence of so people around and it being so open and public, and again, no weapon, patron was at best about to catch a beating, which I think even is a stretch because there was no verbal threats or display of intent to do violence.
Anyway, to your question, assuming the jury is going to disregard the public location and cameras everywhere, if the patron gave the exact same story, I think it would remain unjustified. The shooter claimed that, given the circumstances, he drew the inference that his life was in danger, a danger of serious bodily injury. That’s the standard.
I think there the facts support only an inference of a threat to bodily injury. The shooter could have safely waited before escalating to shooting. Shooting a YouTuber in the chest was disproportionate to the facts, in my view. The proportion has to be objectively reasonable, such proportion as society is willing to accept. I think, if everyone shot in this sort of situation, nobody would like it, and there would be many, many more deaths by gun violence.