Personally, I'm against unneeded violence but I agree, if someone breaks into my house I will act and kill if necessary. I don't care so much for the stolen property or anything, those are just objects that can be replaced if need be. What would make me act is that the robber could potentially hurt or kill my loved ones. Dan is right, you never know what the robber is thinking. So many times people get murdered or raped during a robbery, you never know what they are thinking so you never know what will happen. The only defense against it is to act upon said intruder.
Those who think otherwise are just living in their own fantasy. The world is not a nice place full of flowers and sunny meadows. The problem is degenerate humans, aka burglars, will take whatever opportunity that arises for them. They see your stuff and see your not going to do anything to them, they take it. They see your wife or girlfriend sitting there helpless and see you aren't going to do anything, they take advantage of the situation. I'm only 24, but yes, I WOULD KILL if theress even the TINIEST RISK of my girlfriend getting hurt or worse.
Well said.