TL:DR – do you know the different scripts that violence can follow? Good. When violence is following the “Safe” scripts, there’s a minimal chance of injury, and a maximum chance of getting away without things turning violent. There’s no real need to hit the guy unless you screw up. When you see the “dangerous” violence scripts developing, then just plum drop the BG as soon as you can or as soon as is prudent. If the “safe” scripts start going weird, then it was probably a “dangerous” script trying to masquerade as a “safe” script – drop him as soon as you realise it’s not actually one of the “safe” scripts (preferably before the BG realises that you’ve cottoned on to him).
OK, time for some actual clarification.
Let’s generalise like a SJW for a minute to make a point. There are two kinds of interaction between humans: social (purpose: maintain the social status quo) and asocial (can harm social status quo). Violence follows these distinctions too. Paging Rory Miller. Social violence has a couple different incarnations (monkey dance, educational beat down, status seeking show, group monkey dance). Asocial violence comes in resource and process predator flavours. Of these scripts (or known/”predictable” patterns of behaviour) the monkey dance, educational beat down and resource predation are less dangerous. They’re unlikely to get you killed. A monkey dance might get you some chipped teeth. A resource predator will take your car (and may hit you on the head first). And an educational beat down (unless you violated some pretty hard-core rules) is likely to be fairly minimal. They can go to extremes. They can be taken too far. But you know what’s likely to happen. In a monkey dance the other guy makes big noises and gets up in your face, and all for the good of the audience of female monkeys (because human females surely do not find this attractive – at least, not the kind of human females you want to be involved with). So when someone starts yelling at you, wondering “who the fuck you looking at!”, and starts to come close like he’s going to get up in your face, but there isn’t anyone else around. Then you have to not get suckered into an emotional response (like he wants) and realise that this can’t be a monkey dance because there isn’t an audience. That means this isn’t a monkey dance with a drunk 20-year old. It’s a predator in disguise. Run away. If you’re trapped then drop him.
Remember, a monkey dance normally happens around people, around social places/events, and the audience is watching him as much as you. So if it’s a lonely car park far from any clubs; if the only audience is his friends; and if everyone has eyes only for you. Then it’s not a monkey dance. Get out. Now. That’s how you know whether it’s time to hit someone. (Hint: Hitting someone before running can waste valuable head-start time. Hint: If someone’s between you and lights and noise, then climbing over his face to get there is faster than taking a stance).
In a straight up robbery everyone knows their role (except a newbie to being robbed or a newbie on his first stick ‘em up). The mugger plays it as cool as he can. The victim plays it cool and co-operates when asked for possessions. Mugger leaves as soon as possible to minimise risks (you better believe he does a risk vs reward analysis – it’s called the interview).You behave, he behaves, all is cool. You loose your stuff, but you go home alive. So you hand over your wallet and watch like the guy says, but then he looks around and hesitates when he should be running. Then he looks back at you and looks around again. Why is he checking for witnesses now that he’s finished robbing you and there’s nothing left to see? Why is he not taking the clean escape that’s available (he already checked for witnesses before robbing you and he picked this spot to mug you, so he knows he can escape just fine). At this point you should realise that he’s after more than you wallet. He’s staying there. Engaged, because he’s not finished with you. He’s re-checking for witnesses because he’s not finished with you. He has your belongings, so the only things left for him are torture, rape and murder. This is not the resource predator script anymore, it’s now a process predator script – drop him at the soonest it’s-close-enough-to-an-opportunity presents itself.
The mugger (low level crime, not harshly investigated by the cops) tries to move you somewhere else (exposing himself to prosecution for kidnapping – more thoroughly pursued). Mugging is quick. Hijacking is quick. Even murder can be quick. Rape and torture take time. The only exception I know of is in South Africa where it’s periodically fashionable to mug someone and throw them in the boot (trunk) of your car and drive them to an ATM so they can max out their bank card for the mugger. These people are mostly let go. Mostly. If you’re willing to take the risk that the guys stuffing your girlfriend into the boot of their car are being honest when they say they’re just taking her to an ATM… Well then for her sake, I hope they’re being honest (and don’t change their minds).
This is why it’s important that you know the different violence scripts and practise spotting them. You need to be able to tell which one is coming at you so that you know how to deal with it, and so you know when what he wants you to believe is a lie covering for something worse.
So to sum up:
If it’s something relatively low level, then you can probably de-escalate it (talk it down). If it’s something higher level, you can try deter it (giving off the signals of being an expensive target). But some people will pretend to be low level to make you think that talking it down will work, when actually it’s beyond talking (i.e. sucker you into the wrong mindset). So if the BG does something that isn’t low level, they’ve given themselves away – hit him.