It depends on the circumstances and the individuals own beliefs but in my opinion yes it is justified depending on the circumstances.
Example: Someone breaks into your house and threatens to kill your loved ones, in my opinion it's justified to kill them before they harm you or your loved ones.
Example 2: Someone breaks into your car and nicks the stereo, you know who it is and kill them, in my opinion it would be wrong to kill them for a material possesion.
Overall my opinion is it's justified if it's to protect your loved ones but wrong if it's just material possesions.
For material gain and societal/religious/ethical differences, no.
I don't think morality is a true thing, it's just a human concept, but to me anything that's pretty much pointless (i.e. anything that goes against what I've said) is not worth the effort.
Any concept that mankind has created isn't worth killing for. And I think the same thing goes for animals. We should hunt for them, and use all that we are able. We shouldn't breed them to die, and take what we want.
Put my reasoning this way: is killing animals and cutting down the forests for the sake of the abundance of resource justifiable beyond human arrogance?
If someone broke into my house I would give them a chance to leave before i shot them. I have a .410, 16 gauge, 243, 30-30 lever action, and a revolver somewhere.
Yes. As people have explained, if it's to save someone close to you, friend, relative, or in the military. But for your gf cheating on you, someone stealing something, or just for fun then no.