Lets say I am the leader of a tribe. We have a rival tribe, like oh so many tribes do. One day this opposing tribe has the gall to attack my tribe. An OUTRAGE! Heavens, how dare they? What do I do? I fight, of course. Over the corse of their petty attempt at a raid, they fall to my powerful and well organized tribe. We are victorious. They weren't completely wiped out in the fight, seeing as they are rational, cognitive beings. Well, I cant let them just go on their way, now can I? I have women, and children who need protecting! I can't have them sneaking back in my camps at night and slitting their throats. So, my choices are, bleed them like pigs and let the sands swallow their blood and be done with the whole mess, or I offer them a choice. Serve me and my people, for penance of the crimes you have committed to my people, or die. Its their choice. It may not be an ideal choice, and I'd rather see them all live as servants, well treated i might add, to my people. Does that make me an evil man?