He's ignoring the point that 'rule of law' didn't exist in the Americas. Maybe private property and rule of law existed in Europe and made for a better society there, but the conquistadors that came to the Americas acted like the rule of law was "whatever I want to do, I get to do." Ideas like private property don't excuse things like slavery and murder.

You can't say, "I claim this piece of land for my own. Oh, look! There are people living on it already. I guess I get to enslave, rape, torture them." This has more to do with brutal people being the first people to encounter the natives in the Americas, and deciding that since there was no European justice system or society to condemn/jail then that they could do whatever they felt like.