Just report/BL people if they're going to be that toxic.

I personally won't fault someone for under-performing unless it's obvious they're throwing the match and not even trying. I've had multiple occasions where our healer just gave up and started hopping around and doing nothing just because we had two deaths early on, which is foolish because the Feast much more so then other PvP modes is designed in a way where you can make a potentially huge comeback as long as you're not getting totally steamrolled..