If you are interested in actual "self-defense," the best self defense you can do is not fighting back but paying attention & de-escalating or proactively leaving a situation if it seems like it might be unsafe. That's your best bet by far.
So anyone who "responsibly" carries a gun (if that's possible) ought to be the LAST person to escalate a situation. Anything less means that when you go out carrying a gun, you are *hoping* to kill someone.