Sorry, yes, I did mean to write sapient. I'm not sure that's a conflict, however, as much as further along a spectrum. Whether or not eating cows is ethical is possible to debate because there is valid question about how much of a mind they have but that was never honestly in question for humans. The people who kept slaves had to invent things like the “mark of Cain” theology _because_ they knew their victims were intelligent, feeling creatures like themselves and had to justify treating them in a very profitable way. All of those elaborate “the gods want this” constructions exist to get people to override their natural instinct to recognize someone as a person.