No deadly force was warranted in hindsight. As other have said, you never know if you would have presented a weapon or not until faced with the events.
In the video, the victim seems to be relatively unconcerned for his own safety, continuing to proclaim "I have done nothing to you..." while he could have simply broken a few arms, cracked some heads, or run away. He acts almost like he was trying to parent them or scold them, rather than protect himself. In a state with stand-your-ground legislation, who knows how it would end, especially if this guy was armed and fed up with this kind of crap. The Goetz in my memory was such a figure - kind of like the main character in The Brave One: someone who arms and hunts in response to having been hunted.
He had ample opportunity to run, and could have certainly fled if he hadn't stood, pointing at the kids, mouthing off. This is a bunch of kids acting like bullies, having picked a guy they felt would take the abuse - and they were right. It actually made me think about wilding behavior of packs of chimps. The guy does work at a flower shop, so they might have picked up on his lack of machismo (generalizing here that a guy who arranges flowers is probably not going to appear to be a tough guy.) People prey on the weak and unprepared, and groups tend to get into a frenzy and lose perspective.
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“I WAS ATTACKED AT L’ENFANT METRO SUNDAY AT 7:15 PM. NO ONE HELPED. PLEASE BE CAREFUL.”
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That says it all.
This theme has been repeated since before I was aware of it. Back in high school, I recall hearing about people in NYC and similar places not coming to the aid of others in such situations (to Texans, NYC was emblematic of all things wrong with people.) Come to think of it, we want to get involved, but our CHL training tells us to stay away from intervening as a third party... Chicken s**t laws intended to turn us to wimps now tell us that if we go to the aid of another when we could have run away, self-defense does not apply.