Youy are clearly unfamiliar with the term "Glasgow Kiss"
I'm familiar with it. I've seen it happen plenty of times. I used to live above a really rough pub in a really rough town. Some of the things that I saw out of my window were unbelievable. A guy getting his head repeatedly kicked into a metal railing, several bitch fights, guys getting slashed with bottles, police getting attacked. It really was great entertainment.
I've never given anyone a Glasgow kiss though, and thankfully I've never recieved one.