While I understand your frustration, this really had nothing to do with the gun show rule. I hate the rule as well. This is an idiot who shot himself in the leg, nothing more. If allowed to carry loaded gun at gun show, this is the same idiot who would pull it out to try holsters.
I have unloaded/loaded dozens of guns, hundreds of times and have yet to shoot anything I wasn't intending to shoot. The gun show rule is not at fault here.