How Can I Stop My Boyfriend From Being So Mean In Front Of His Friends Towards Me? Please Help? I'm So Fed Up!?

Every time that he is with his friends and me at the same time he acts like such a jerk! He'll try to act all "cool" and he'll agree with whatever they say. He usually isn't mean to me but the part that gets me is just that he doesn't defend me. Like his one friend was like, "Damn Dana, you have got the all time weirdest fu(king haircut I've ever seen in my entire life. And you dye it don't you?" And Chris (my boyfriend) just sat there and didn't say anything. and we have Co-Ed so when I made the 3rd out in softball they were all like, "Man, Dana, you su(k at this game. Were gonna lose with you on our team!" And once again, Chris just sat on the bench and gave me this look than looked away. It's really really really irritating but I don't even know he realizes I want him to tell his boys to cut it out. What should I say that won't get him mad or sound accusing?