Murder is taking a life without warrantable cause, which correlates to what you said, “Some killings are justified, some are not.”

But such killings happen every day, do they not? And I would daresay that what one person considers “warrantable cause”—He was raping my child; She was having sex with a man not her husband; He didn’t show me enough respect; The baby just wouldn’t stop crying!; She brought shame upon our family—another will not.

I think that in each society there is some “universally preferred standard of behavior”, and much of that derives from the concept of rights, so again, the idea isn’t useless. But I believe it is not helpful to expect that everyone’s conception of them, nor actions based on what they are, will agree with one’s own.