Seems like overall poor sittuational awareness by the victim. To let someone stand that close to you after aggressively coming on your property after a verbal altercation, and not be ready for a physical assault. The haymaker that guy threw would not have been hard to block, deflect or see coming.
If you are going to run your mouth, be prepared to deal with the consequences. That just being a tactical critique, in no way blaming the victim for the actions of the attacker. Just saying he needs to wake up a little. Probably will after this.
But if you handled it properly, you could be totally justified. Tell him to get off your property, keep your distance and draw. If he keeps coming his intent is clear. Would you be ok to just whip it out and shoot him while they are standing there like at the start of the video? No, but if he had handled the whole sittuation better, he could have been.
Absolutely right - that guy was WAY too close to the victim. I wouldn't have allowed him to get that close, even if it meant I had to back away. Elevated tempers, just no reason to be that close, and not also be completely in defensive mode.