It seems to me like you never actually took another person's life based on how you expressed your reasons to commit murder. But in fact, murder and killing someone are not exactly the same in the eyes of the Law. Simply put, murder is not a reaction to or because of something, it's a willful intent and action of taking someone's life. The easiest exception to this principle is War. I'll get back to this in a minute.
Now, Freedom and (social) Justice heavily plays into the making of this law, this rule. In fact, almost every society on this Earth has some law/rule pertaining to murder and theft (and taxes too, ugh!). In the US where I'm from, we have this idea of these unalienable, i.e God-given, Rights. A sort of freedom that no one could, nor should, try to limit or take away, the from expressing such a Right. And the first pf these principles mention in the social contract (the US Constitution) between people and government is "life." We have the Right to life; to live. No one should take it away from us, not even our government, our neighbor, or pope, or rabbi, or guru, etc, etc. Therefore, BECAUSE I LIVE in a society, and community of such thinking, its implied that I agree to abide in certain behaviors and conduct derived from said Social Contract; from said Law. So if I rebel I be braking such a social contract (the price to pay in conduct to live in society), I would be braking the Law.
When it comes to taking a life, it is never about my perceive notion of in/justice. It is about exercising my Freedom to life, it's about defending my life, and/or that of my family's, specially in my own home and dwelling. So, given a situation where I perceive/know that my body/life is in immediate danger from the action(s) of a person/people, I exercise my Right to live by using any force necessary to neutralize the threat to my life, to include using lethal force. This Right doesn't mean I can flaunt this around for my own vendetta, it however does cover me from the Law as to NOT limit my Right to life. As Gerkak already mention it, this is called: Self-Defense.
The idea of Self Defense is about self preservation, it's about living. And just how corporations can be seen like a person hood in the eyes of the Law, Countries, Nations, see themselves in the same light as well, though, this makes it more abstract and complicated. Thus War. War then, in a sense, becomes violent actions of self preservation between two or more countries. The self preservation can be in the form of: protecting their way of life (culture and community), often heard as Freedom; national financial interest; power; and influence, to name a few. So in a way, the military is the physical manifestation of the body of said country. Strangely enough, two armies fighting in a war is analogous as 2 people having a brawl. And in a way, casualties in war are like bruises in brawl fight. Man, like, I said. it's complicated.
I used to think and act like you. So I don't blame you for your thinking. Actually, I'm glad that you have the guts to at least express it, even if others disagree (including myself) with you. But then I joined the US Army. I went to war. I'm a veteran now. My combat experiences taught me oh so viscerally of the fragility, and preciousness, of life. It is precious because it is fragile. It's the evil in our hearts that needs to change, not which life that should end. And we, as individuals, don't have the Right to say who dies or who lives. We brake that social contract if we do (braking the law, braking the law, braking the law!) Narutojunky talks about how this idea was thrown even in Naruto in how to end the cycle of hatred.
Anyways, thanks for reading, just giving my 2 cents. Peace.
