I disagree. Why? I **** you over in nature, what do you do? Kill me. Or get someone else to kill me. Therefore, unless I can truly and utterly obliterate you and anyone who might take umbrage to said obliteration, I treat you with, at worst, indifference. In civilization, or at least in the civilization in which I find myself, awful behavior is rarely punished. If I figuratively backstab my coworker I don't have to worry that he's going to literally backstab me, or really do much else but perhaps attempt to screw me over in some capacity later on down the road.
Civilization opens the doors wide for shitty behavior. A little barbarism, however, tends to clear that right up.
The key to using people is knowing how to do it in such a way that either A, they don't even know they've been used, or B, there's nothing they can possibly do about it.