Back when Europeans first started to conquer the new world, the world was still firmly in the Malthusian Trap, where populations were up against carrying capacity constraints (at the extent technology levels). I think this had pernicious effects on societies. Excess population made people expendable and callous. It would not have been easy to try to convince people to allow Others their rights.

I don't think it's a coincidence that this flowering of democracy and liberalism occurred in a context where conquest had opened up land to expansion and had at least temporarily relaxed the Malthusian constraints.

Please tell me which of the tribes that lost land to the US never stole land from another? Please show me a land in the world that never had slavery. Please tell me the origin of the English word “slave”. Please explain what your last sentence means.