It seems to me that you're simply defining "aggression" as "unjustified acts of violence", with the corresponding assertion that justified acts of violence are "non-aggressive", regardless of how, well, aggressive it actually is. You're not actually talking aggression and non-aggression as qualities of human behaviour, which would entail trying to discover the nature and origins of violence in human society, you're simply explaining when you think cracking skulls is justified and when it is not. And if you'll permit me to be a bit cynical, you're just calling it "non-aggression" because that sounds like something a libertarian would talk about.