I've got a younger brother that's does these things also. He's 30 years old now and still doesn't give a fuck about anyone besides himself. My kids know to ask an adult if my brother tells them it's ok to do something.
It truly is sad... A couple years ago him and I went out drinking at the bar. Some kid wanted to beat his ass and we had mutual friends. So out of respect the kid asked me what my thoughts were. I told him to not break any bones and don't knock him out so he feels the pain. Sure my brother was upset, but it was something I had wanted to do to him for a while too! I made sure he didn't get hurt and that was about it. We all need a good whoopin from time to time! Kinda like a hangover, reminds us why we do things in moderation.