Welcome, ShT!
Not to be too forward, but does that mean something else in French? Seems like you're missing an i....
I need to address something Osan said - about south central LA. The thing you need to realize is that California is not a gun-friendly state. There are large metropolitan areas with bad reputations in the US - LA, NY, DC, and Chicago. I don't think it's an accident that all of these cities are in areas that are gun-unfriendly.
I live in northern Virginia, right next to Washington, DC and almost on the border with Maryland. Virginia is among the most gun-friendly states in the US. Maryland is among the most gun-UNfriendly states, and DC is worse.
The only thing that separates gun-friendly territory with un-friendly territory here is a river.
Once you cross that river into Maryland or DC, you find what you find in New York or LA or anywhere: areas that have a lot of money are safer than areas that don't have a lot of money, but even the safe areas are a little sketchy.
But in Virginia, I've never feared walking through the wrong alley.
To answer your question, I seldom go anywhere without a pistol.
I carry it concealed, which requires a state-issued permit. I have the option in Virginia of carrying it openly - that is one reason Virginia is gun friendly. You can walk around with it strapped to your hip with no permit required, and most police officers aren't going to even question it. I choose to conceal it because of other citizens' perception of it (people are just not that enlightened).
Plus, I think of myself as what we sometimes call a "sheep dog". Just as a sheep dog sometimes gets confused with the flock, and only shows his fangs to frighten off the wolves - so you will also find ordinary citizens here who are capable of killing a wolf if the need arises. And in the same way we don't harm the sheep. But criminals are not wolves - they are people. And even though they can't tell where the sheep dogs are, they know they are out there, and are not likely to take actions that will get their brains blown out. It doesn't take many sheep dogs to make criminals think twice.
In order to get the concealed permit here (many other states have permits as well with similar requirements) I had to show that I had some rudimentary training in shooting. Military service counts, and hunting licenses count, but most people choose to take a specialized course in basic pistol which is designed to train people in how to carry.
The course I took (it's an NRA designed course) spend just as much time on going over when it's ok to shoot and when it's not, and different legal issues, as they do on actually handling the firearms.
(I think it's important to note that the system is only concerned with safe handling of firearms, and does not require citizens to learn anything about the law or whether they're going to jail for shooting someone in their particular situation. This is something the market developed without state interference.)
So the point of all that: the majority of sheepdogs - overwhelming majority - have knowledge of when it is appropriate to end a life and when it isn't, and are also aware of what is likely to get them thrown in prison and what is likely to result in their walking free.
Shooting someone for getting slapped in the ass is likely to get you thrown in prison.
But it's going to depend on the circumstances of the case.
If the woman was getting repeatedly slapped in the ass, or if the man was moving on to other things like groping her breasts, then in Virginia it would probably be ruled as justified.
If the guy had lots of friends, and they were all doing it or surrounded her, then it would probably be ruled justified. (Unless he was secretly a cop, but that's another story.)
One slap and then bang-bang corpse? No, she's probably doing time.
Of course, the complication is that most gun owners/carriers know that if they shoot someone, they're at least going to have the gun confiscated, they might be spending the night in jail, might have to post bail, will probably have to defend themselves in court, et cetera - meaning that ending someone's life is an expensive prospect, both in money and time, and the shooter may also suffer a considerable loss in reputation. It is very, very expensive to kill someone, even justifiably. The law is very specific in most states that it is only justified in cases where the shooter is about to lose his life or suffer gross bodily harm. So the shooter needs to weight that: is what's about to happen to me at the hands of this criminal worse than what the state is going to do to me if I shoot him? If so, then bang-bang.
The other thing to remember is that having the barrel of a gun pointed at your nose tends to alter the situation immediately. If she got slapped and then brandished (technical term), then he probably is going to put his hands in the air and back away slowly. John Lott of the University of Maryland (look up his books) has estimated that there could be as many as 2 million "defensive" uses of firearms every year, where all that needed to happen is showing the assailant that the victim is armed, to stop the situation.
I hope this helps, and welcome to the forums - stick around and listen to us ramble.