Sounds like an awesome friend ! Kicking someones ass, while satisfying, is usually not an efficient way to solve a problem. Often you'll just cause yourself more headaches, I know this from an experience I had in my early 20's. Lots of headache, and the issue still existed.
I say, start dating the girl again, fuck her in every imaginable orifice, with any bodypart/object that will fit (comfortably of course, shes not a machine). Videotape said excursion, and send to him in mail. That'll fix your problems !