I see what you are saying here and I agree to a point. If a guy is just punching you in the face you can't legally shoot him anyway. The situation will determine what your options are in the end.
I think and have seen that in any given scenario if somebody really really wants to kill you or hurt you, then they will have a pretty high success rate if they don't care about the consequences. I do practice open carry. It is legal and convenient in TN. I walked past two cops this morning inside the gas station, they never even flinched. I work as a process server as well so I carry openly doing that damn near everyday.
I get different reactions from different groups and areas. some people just hate cops and I look like a cop doing my job. I see the gun as a deterent for the most part but some people will just come at you anyway especially if they are more on the wild/hard side. Basically they just don't give a fuck and want to try you. I will say when you knock on someones door you get more respect wearing a gun than not. I have tried both ways. I also don't have to flip a shirt or coat or anything to get to my weapon if I need it and that is worth it to me.
That being said. I would not automatically go to my firearm for defense. I get more enjoyment from beating a dudes face anyway and I spend less time in jail and smaller fines for it. Guys who say they would just shoot some guy who played the knockout game on him is and idiot. If a bullet leaves your weapon you are responsible for its effects. Even if you don't get charged criminally, which you would, then those kids parents are going to sue you.
If I sense a situation may occur I just try to stay away. If I can't avoid it then I keep my eyes and ears open and all the bad guys on one side of me.