I do the only thing you can do when someone begins to team kill… leave that game.
When Playing Call of Duty 4 (PS3) I was in a hardcore mode game that had friendly fire.
Two players on my team kept targeting me instead of the other team. At first, I criticized them that their team killing would keep us from winning. They kept killing me, so I left. Perhaps I gave them pleasure by leaving, as they knew their actions caused me to change my gaming experience, but I was not going to be on the receiving end of their poor sportsmanship.