That's not your definition of self-defense, but it fits many legal definitions. It says he left his vehicle to verbally challenge him. It also mentions he tried to deescalate via discussion:

Witnesses said that Warren had attempted to discuss the matter before things became violent and that he appeared “exhausted.”

He left his vehicle to discuss then the other man threw a punch, at which point he hit the guy back only only once. If someone is yelling and swearing at you, are you supposed to run? You can't even attempt to talk it out or you lose your right to self defense?