fvck that, why put up with people talking sh*t? Next time you see him, walk straight up to him, tell him if he wants to talk sh*t he better say it to your face, and if he doesn't have the balls, crush him.
"I can't confront him, since that would cause some emotional-upheval in our group of friends (you know, that sh*t with secret telling)... " - sounds like a bunch of b*tches if you ask me.
nearly any amount of disrespect can kill your game with the ladies, don't stand for it.
check out the post from stockholder in the bible called "evil ways"