"Sin lies only in hurting other people unnecessarily. All other 'sins' are invented nonsense." --Robert A. Heinlein
Just because murder is a sin to you doesn't mean it is to another. And who wants to be the moral arbiter on "unnecessarily"? What if I find it "necessary" to hurt others who "impede upon my own happiness"? Who is Robert Heinlein to tell me I can't do that? Who decides these moral questions?
Only One Being has the right to make a Universal Judgment on issues of sin and right and wrong and his name is not Robert Heinlein.