You'll notice that I did put the word "fair" in quotations. A predator won't kill someone unless they are a threat, or armed with a weapon. Both mean pretty much the same, but I wanted to cover all sides. A better way to put it might be the have rules and Aliens do not. Still, it is a form of being fair. I'm not sure why it is questioned. The 1st Predator movie shows what I am talking about. It did not kill Anna because she wasn't armed. As Arnie stated in the movie. And the very end when Arnie used up all his home-made weapons, the Predator discarded his sholder cannon. A little hand to hand combat between the 2. Fair to the point that they had no weapons, but not at the same time because the Predator is HUGE and 10 times stronger. He only tried using his blade when it appeared Arnie was defeated.