i'd hesitate to just call it a shove. That was basically a sucker punch, as far as shoving goes. The shooting in self defense was justified in my opinion, although the shooter potentially has consequences he must now deal with.
I'm not sure what other options he would have had other than draw and shoot if he wanted to protect himself and not become a victim.... Brandishing a pistol without using it is a bad idea. If he got up, he possibly would have gotten jumped and beaten. The other individual's reaction to the argument over the handicap stall was already WAY out of line. And the fact that he just attacked you and put you on your back, 20 years younger, bigger, and aggressive justifies deadly force if that's all you have available to protect yourself with. On the other hand, if it was a 90 year old grandma with dementia that tried to push him and she ended up on her ass, no he wouldn't have the right to pull his gun and plug her.
So it's harsh language considered a use of force? Can i fear for my life (and subsequent deadly force) based on a stern look, threats, and/or being shoved? I guess that depends on what State you live in.
shooting someone in self defense is always a last resort, as it takes the consequences for that action out of your hands. whether or not its justifiable is subjective and is up to the interpretation of the law by the court, jury, cops, prosecutor, etc.
My guess is that if it was merely words, shooter be sitting in a prison cell. If the shove was a weak-ass one handed patty cake push (instead of hard enough so he went flying to the ground), shooter be sitting in a prison cell.