Yeah but you wind up with pretty much the same problem. We say no or the bartender says no and you still wind up out the front punching on with the guy.
Meanwhile the patron is in there to get drunk. They pre drink before they go out. They smuggle drinks in,hide when they are drunk,get their friends to buy the drinks for them. If they get caught they will argue and fight to stay in. Once they are out they will trespass to sneak back in.
It is a scenario that is about as us them as you can make a scenario.
And in a fight it is a pretty even match. We are not protected by law do not have defensive tools and in gener have to fight people without hurting them.
All things that are very possible. However, the bouncers in my area, aren't there to trade punches with some drunk idiot. If the drunk idiot, is still being an idiot after being removed, then the cops are called, and they're arrested.