I think Aristotle had the greatest mind of any human who ever lived. The older I get the more I realize that there are a thousand true and intelligent things you can say about any topic. Magazines, journals, and libraries are full to the brim of intelligent people writing intelligent things. But an extremely minuscule portion of that huge mass is made of writing that gets right to the heart of the matter. And Aristot…
Great mind? I don't think so. https://en.wikipedia.org/wiki/Natural_slavery
Note that I'm assuming an objective/neutral definition of "slavery", and not the usual "slavery=bad thing".
Now, we could argue that it's a matter of education, circumstances, etc. But surely you must have met people who would obstinately refuse to listen to reason, entertaining their own misery. At least IME, it's sadly a common trait.