Well, the definition of murder is to kill unlawfully, and there are laws in place throughout the world that limit the right to kill under certain circumstances. For example, here in Sexeland, provincial law forids killing a clergyman on sacred ground, a captain on his ship or a legitimately-conceived infant below the age of five months.
So posit instead that the definition of murder is widened significantly, I'm not sure how significantly, maybe there would need to be some kind of universally-agreed upon legitimate grievance, or maybe even a blanket ban on the killing of certain kinds of people, (women, children, the elderly, etc.)
One certainty, according to the theories of Carolus Daruian, is that our race would be much weaker without the constant weeding off of those who can't defend themselves. The physical difference between the people of the Orient, (who relied on state intervention to settle their grievances), and the people of the Empire of the Entire Universe, (who had engaged in mortal combat for centuries), at the time when contact was made was huge, and probably helped ensure the domination of the former.