Self defense. But also like someone else said proportionate response is key. If someone gets mad at you in a bar and throws a punch, pushing him away is fine. Hitting him to subdue him is probably okay. Shooting him dead is not.
I'm also not really okay with people using murder to defend their stuff. Like if someone sneaks into my house and I catch them going out the window with my tv, shooting them is not to me justified. There are more TV's. That guy gets one life. Remember what Gandalf said.
I think a lot of people have like tough guy fantasies about shooting a burglar and it always makes me uncomfortable.
On the other hand, if someone was on trial for shooting a Nazi dead I would find them not guilty. Shame that Nazi spontaneously bled out. But at least he's gone before he killed my entire family and friends.