What should i tell him?!?

I have a guy friend and we are really close. Most of his friends are those "cool" guys who get bitches and dump 'em and drop out of school and crap lke that, but he is different because he actually treats women well and is respectful. But latley he's been trying to act all "gangster" like them. He acts like he doesnt care and when i talk to him he disrespects me and its really annoying. I think his friends have gotten to him but i dont want to act like his mother. what should i do/say?