Why would anyone be on Chris Brown's side?

I haven't been following this thing all that closely, but it seems like a lot of ppl are making light of this whole thing and even blaming Rhianna. No matter what your opinions on the matter are personally, is there anyone that can give me a summary of what supposedly happened between them? Someone said in recent yahoo post that she supposedly gave him ? Another someone said that she started the fight? I watched some spoof on Youtube of the fight where they are arguing, she gets all up in his face hit him, then he barely touches her and it cuts to a scene of her with a black eye(done with intentionally bad makeup). Seriously please someone explain whats going on?