I think you and I are coming from very different sets of assumptions. Before answering your questions (all three of them
) I'd rather have a better idea of where you're coming from.
I should also apologize for my rather imprecise language. I should have said that your argument seems like a rather lame justification for killing a person. "Murder" has too many connotations.
My initial reaction is as follows:
A sound justification for killing somebody might be self defense, or protecting another person from immediate harm or death.
Legality is very important, and (in aggregate) tends to help provide justice. Neither has much of anything to do with destiny. But how can anyone know their own, or somebody else's, destiny?
Killing the body to save the spirit is a dangerous proposition simply because we can never know if the spirit is saved.
Governments make decisions of life or death as a basic compromise necessary for dealing with violent, deviant behavior. Lack of such institutions make any form of society difficult to maintain. That is, any society must figure out some way of dealing with its deviants. Many, in fact, do not put people to death. But there is an ethical and moral difference between the citizens of a society (or their representatives) administering justice and a lone person taking that responsibility on himself without the permission of that society.