Infighting

I'm finding that I may have to lose a couple people standing up for one that I haven't exactly gotten along with. Honestly, inside the group of people I hangout with, I'm usually the mediator. Now my brother and my best friend have been acting like complete assholes to Lou. I know me and him don't always see eye to eye, but I have to do something. They are, as my one friend so eloquently stated, "A couple of egomaniacs". They think they are better than everyone for several reasons. My brother thinks he's better because he's that physical jock type of kid, and he thinks his muscles will get him anything from a girl, to a victory in a fight. My best friend seems to think because he spent one semester at college, he's so much wiser than me. Now the kid isn't dumb, and I'm as pissed as him that he couldn't finish, but he is in no way smarter than me.
Anyway, this whole thing started, like most petty arguments, over a girl. Lou recently got back in touch with an old friend from years ago, and made plans to meet up. Now my brother, being the cocky prick that he is, and my best friend decided that they would go with him, "secretly" planning to try to steel this girl away from Lou. When I stood up for him and called my brother a cocky bastard, both of them, including my best friend, turned it around on me. They began to insult me; calling me gay because I haven't tried to fuck every female friend I have, a future failure just because their plans didn't work out as they wanted, and just all sorts of that bullshit. Well, I'm done with it. Me and Lou argue as much as any friends may, but he has always been there. Hell, when my oldest brother had nowhere else to turn, Lou took him in! Idk what the point of this is, I guess I just needed to get it out somehow. I hope I can do this without alienating my best friend, but if that's what it takes to make him realize what he's become over the last year, then it is going to happen.