My ex had numerous scars from bulletholes acquired during a New York convenience store robbery. He was in a coma for weeks, he told me. He also told me he'd tried to talk the thief out of robbing him - the sort of hamartia that ended our relationship; he could be so damn maddeningly annoying when he opened his mouth I felt like shooting him myself at times. I'm a little more civil than his robber.
I've been held up, had a pistol in my face at an all-night diner. As I came out of the men's room, I immediately recognised that there were four men in stocking masks in the store, and one of them had my manager on the ground with a pistol against his head. A barrel spun around into my face and a voice said, "be cool, man." I was cool. The police trashed the place fingerprinting and whatnot, and we opened back up in time for the bar rush - a crowd with a history of rudeness to the servers. I quit the next day. The owners had had video cameras installed, and posted signs to that effect, because of the number of times that particular store had been robbed. Police never caught the guys who held us up, and the security cameras were obviously not much of a deterrent.
It's a scary feeling to have a gun in your face. I felt helpless, and later - furious.
Giving up the money (or goods) is not much of a deterrent, either - as has been said, the reason that's recommended is for the victim's safety. But if you've been robbed several times already - I believe I understand how frustrated and angry that couple must have been when they realised it was happening yet again. I will never know for sure, but I can't help believe that the head-kicking expressed not just an enraged desire to punish - but also to deter future would-be robberies. I just hope that the thing their robbers learn is not to come back with guns next time - then the store owners would have participated in what my ex calls "schizmogenesis" - an escalation of conflict.
Yes, I understand the idea that the woman was being excessively cruel, kicking their assailant when he was (arguably) down like that, but he was already in violation of the social contract that prohibits such behaviour. And, yeah, okay, I know that an eye for an eye is what Jesus Would Not Do...
But I get them, I really do. There's no way I'd prosecute them. If I were in their jury; I'd never convict them.
And honestly, I can't say that I'd behave any "better," were I in their situation. - Oh, wait - I was. Nope. I'm no better.