Dak
mentat
I think you are sort of ignoring the idea of barbarian culture vs. civilized, in the eyes of Europeans at this time. We are not fortunate enough to find white examples on an unknown continent who we enslaved, but I think the reactions differently to NZ/Aus show this kind of barbarian/civilized mindset, rather than darker than me idea
I agree, and this thinking is not limited to White Europeans (barbarian is Greek in origin, and originally mocked foreign languages). The Germanic "barbarians" that finally overran Rome weren't considered "barbaric" because of skin tone but because of cultural and language differences.
The distinctive racism surrounding the Atlantic slave trade was an unusual aftereffect of a peculiar situation, and not simultaneous.