Loitering teenagers doing pretend karate kicks at girls

I was leaving a shopping center last night, when outside it, there were these two teens loitering (male & female). It's funny because I knew it was going to happen before I passed. He did some sort of kung fu kick, pretending to hit the girl in the face. She laughed at it. I know they say girls are impressed by fellas who have natural contempt towards them, but seriously!

Perhaps you could say it's none of my business, but what's with this? And why did he do it, just as someone was passing? You see it often. I don't like it - perhaps because the passer has to account for worst case scenario. It's not exactly something you'd see in a movie with Sylvester Stallone walking down the street with something like this occurring in the background!

Supposing I had said "don't be doing that lad"? Nothing probably might have happened... or he might have just thrown a sweet or something at me as I walked on. Hmm