My BFs best friend?

when ever he comes around, he becomes a big jerk. a few days ago he responded to me "no duh". I have tried talking to him, but e doesent listen. i asked him why he likes him, and he dident say and he dident want to tell. yesterday i tol him that he was being a big jerk whenever his best friend comes around, and he said he wanted to be cool like him. any ways ican help him out a bit?