>Many things are naturally repulsive, but are indulged out of necessity or gain

Most "naturally repulsive" things were accepted just fine in one society or another.

Aristole spent time to defend and rationalize slavery because that was just job, to spend time rationalizing things. Other societies practiced it with no such worries, and found it perfectly natural.

But even if we grant you your "naturally repulsive" actions existing, it doesn't mean they are objectively morally wrong. Just that their moral judgement is not just based on culture and historical period, but also on evolutionary adaptations. These could very well be considered fine in an earlier/later evolutionary stage (in an earlier one, for sure: animals don't have such qualms).

His arguments were generally driven by logic and reason, not rationalization. Rationalization is generally only necessary for adopting views that seem ostensibly inappropriate, which would certainly include these sort of 'naturally repulsive' acts. And indeed his arguments for slavery were some of his weakest precisely because they were uncharacteristic rationalizations.

I completely agree that if you go back far enough in the evolutionary pipeline then my claim becomes invalid. I also think it would not apply to people of a sufficiently reduced IQ. You need to have a minimum of intelligence to understand what you're doing, alternatives, and its consequences on others. But once you have that baseline of IQ then I think morality, and a natural repulsion to certain behaviors, comes as naturally as communication.