In other primates...
Fistfights take place a lot farther along the escalating agression line than the kinds of gestures that most resemble firing a handgun.
A fight usualy goes through a fairly predictable escalation, which is pretty well standardized throughout the higher primates. There is a fairly high probability of the encounter breaking off at each escalation point - on the order of 50%. In other words, about half the time that a primate or group of primates starts screaming at another, that's the end of it. And about half the time that they progress to aggressive gestures, that's the end of it. And so on.
Shooting appears to me to be somewhere between aggressive gestures and throwing shit. Which is several steps short of full contact with injury (fistfight). When a fight is just a matter of non-thinking primate behavior and not really about anything (which I think covers the vast majority of cases) there is shooting long before there would have been a fistfight, and therefore in many cases where there would have been no fistfight, because throwing shit (OK, that's rare in humans, but there are substitutes) would have been enough, or shoving, or wrestling.
And the peacable individual who could most use the equalization is less likely to pack heat than the fighter. The fighter goes out knowing there is likely to be violence. The peacable guy goes out out knowing he's very unlikely to need equalization.
