Now, I agree that murder--which I would define as taking the life of someone for nothing but selfish convienience or killing because of a strong emotion--is ALWAYS wrong. But not all violence is murder.
Shooting someoen who's trying to kill you and/or your family isn't murder. Killing a solider in a war isn't murder. I don't hold it against any German soldier in WW2 for killing a US soldier (or of course vice versa) because that's what war is. Doesn't make it okay, or good, certainly. It isn't what we want to happen, but sometimes violence is the only thing that works because violent people understand nothing else.
Just look at the war on Terrorism! You think Hussein or Bin Laden would sit down and negotiate? OF COURSE NOT. To suggest otherwise is the utmost fallacy.