So...
We can see, witness, and easily prove beyond a shadow of a doubt that the empowerment of the Individual Sovereign Human Being is paramount to both a significant reduction in victims and an overall reduction in the criminal element...
The most effective "justice" is the immediate repelling, destruction, and elimination of all the variations of perpetrators...
Better to be judged by 12...than carried by 6...
Rape victims who arm themselves after the first rape...and then repell, destroy, and eliminate a second rapist...don't consider the second outcome more traumatic than the first...
What's that got to do with eye for an eye? Self defense is completely non comparable to actively seeking to revenge kill when it would not help save or protect anyones life.
Moral relativism is a sham, killing someone is always wrong unless its in self defense. Even if they rape and murder you're whole family, its not okay to track the murderer down and shoot them in the head in the middle of the night.
Now you'd still be a hell of alot more moral than the murderer, but who wants to live a life merely at the relativity of others actions. Either an action is immoral or its not, whats going on around and what happened before doesn't change that (except for in your head).
Killing becomes moral in self defense because your rights are being directly infringed and the only way to reinforce your right to life is to expel the infringer, from life or from your general vicinity. As long as someone is directly threatening your life then it stays in the self defense zone, as soon as they put their weapon down and walk away it becomes plain murder if you want to kill them.
Revenge murders/death penalty takes away all our rights to life. If its okay to murder a man in cold blood, then certainly it can be okay to kill 1 man to save 10 men, or invade a small country to save the world. If eye for an eye is based on doing bad things means its okay for bad things to be done to you, then doing "good" things is always preferable to the "bad", and then it is left entirely to the person in question to decide who gets to die and who gets to live.
Either there are an objective set of morals and rights that don't change on the circumstance or there are non, and it is merely what you, me, "society", religion, or whoever decides it is. Self defense is not a case of murder being okay in a different situation. Its a defense of your rights, murder is any time when you kill when it wasn't to defend your (or anothers) life from direct aggression.
Self defense = moral. Restitution = moral. murder = always immoral