Also the fact that everyone alive today is so as a result of either being on the winning side of colonialism or from their ancestors otherwise clubbing somebody else over the head.
That's a poor justification for it, though, and I don't want to live in a society that goes out of its way to view itself as Hobbesian.
We're all winners here and that's far better than the alternative.
Also the African slave trade largely existed off the back of tribes conquering each other and selling the losers into slavery, which is also commonly how slavery works back into antiquity. The alternative to being sold into slavery is that they kill you.
And it's like this for your village and your neighboring village and their neighboring village and so on.
Tell me about it when your neighboring villages' adult men are charging down the hill at you, filthy, starving, crazed and screaming at the top of their lungs, axes in hand.
Well that seems a little silly, no? Humans are social creatures; cooperation is just as natural as any other human behavior (including fallibility). It seems almost a little christian in its doomful profession that humans are only our worst attributes.