Actually, if someone says "Gimme your wallet or I'll f you up", is that not a form of assault? You don't need to immediately shoot them. If they're a distance off yet, (30 feet) and walking towards you, one can always draw and cover them, with a command voice while backing away in a zigzag. If they're not armed, and not totally up on drugs, they're likely to flee. Even their slow wits often pick up that they've just made a serious error in the victim selection process, and they now have a train tunnel of a barrel staring at them. Just be ready to fire without hesitation if they appear to go for a weapon or rush you.
The finger in the pocket looking like a gun is not so much of a threat if you're moving. They can either shoot badly from the hip, or if they draw, you can fire while they're still drawing. I believe it was found that most thugs who do the finger thing really don't have a gun at all?
But if you see them off that way, if they flee, you IMMEDIATELY call the cops, because you don't, they will and report that you attacked them. You have to call first.
Of course, I also carry a 30-foot-range twoshot OC device. (Kimber put their brand on it, it's flat, and wow, does it have range, it's more like a chemical reaction rocket blast than an aerosol...just be aware of wind direction!) If someone is drunk and belligerent, they'd just get that. Nonlethal.