Ultimatums

What do you do when both your boyfriend and best friend don't like each other? My boyfriend (dated once for 6 months 2 years ago and now for 7 months as of this time) hates my best friend and has gave me an ultimatum countless times to choose him over her and stop being friends with her. My best friend (of 3 years) has NEVER asked me once to choose her over him and stop dating him. He has said he doesn't want to be with me if I am friends with her. I pretty much have already chosen to let my boyfriend go. This was a problem in our relationship 2 years ago with the same best friend. I just want to know what you guys would do in this situation.