Murder unless in self-defence is wrong, no matter how you look at it.
So, how would you classify a mother that killed a person that she perceived as threatning the life of her baby?
What are the basic morals that apply here?
I made a mistake. What I meant to say was: Murder unless in defense of life and property is wrong.
You made no mistake. Self-defense includes defense of others and defense of property.
The problem with claims like "murder, unless in self-defence, is wrong" is that "murder" already includes elements of wrongfulness in it and self-defence already includes elements of rightfulness in it.
For example, I shoot someone because they were trying to take a car. Is that "murder, unless in self-defence"? Well, yes if it's his car but not if it's my car. So you can't even make sense of "murder, unless in self-defence" until you already have a full theory of rightful ownership of property.
Someone needs a job at my store or else they'll die of starvation. I don't hire them because I want them to die. Is that "murder, unless in self-defence"?
Someone needs a kidney transplant or else they'll die and I have the only matching kidney. I decide not to donate it. Is that "murder, unless in self-defence"?
This is the problem with the NAP. It seems simple and seductive. But you can't actually determine what is or isn't "aggression" until you already have both an absolute notion of property rights and a notion of a scope of moral authority.