I'm going to ask my bf to stop hanging out with his best friend.
Why should he stop hanging out with his best friend?
The guy annoys me. He's very nosy and self-centered.
I understand that you don't like your boyfriend's best friend, but it's inappropriate to ask your boyfriend to stop hanging out with him. I suggest that you just avoid your boyfriend's friend, and don't talk to him.
Easy for you to say. I want him to admit he needs to make changes in his life.
It is not your place to make that decision for him. If you are unhappy with him, you can always break up with him, but let him make his own choices.