Why are we not allowed to kill

[Meneldil]

Doesn't the simple fact that by killing someone, you put an end to his life even though he doesn't want it, and then have no way to change what you've done pretty much explain how and why killing is bad?

None ask a murderer to have remorse. I don't, simply because what is done is done, and remorse or not, nothing is going to change it. But on the other hand, the murdered might have appreciated to have a voice in the matter.

If, according to you, there's no reason as to why killing is bad, then what is bad? I'm somewhat puzzled here: are you being cynical or are you trying to push relativism as far as possible?

Edit: this was directed at AdrianII.

Don, let's assume that human beings don't kill eachothers simply because they don't want to spend their time protecting their back or seeking revenge (ie. out of a pure rational and self-centered thinking). Would you consider that as relying onto morals?