Your apology involves an inversion of cause and effect.
The "looking down on the people around [me]" "out the gate", was me criticizing people for peacocking about how much they hate slavery and the trope as it exists (in abundance) in modern fantasy manga, knowing full well they were never planning on making any more substantial conversation than that.
Bro, peacocking is saying "um actually, John Brown could have done better". While that's true, it's lazy argument to make and you are avoiding the main critique many people are expressing here by straw-manning them.
It's not the fact that there is slavery in this manga. It's the fact that the manga is not interested in exploring slavery in any substantive manner; it's being used as a tired old trope in order to portray the hero as 'good' in one of the most lazy and hackneyed ways I've seen to date. In fact, I wouldn't have dropped it if the hero actually freed the slaves. Sure it's lazy too, but holy damn would it have been less cynical than this crap. It would have shown the author having some self awareness in the fact this manga isn't highbrow literature and people would like to see the hero do something actually good. Instead, we have the hero buy a sentient being as if they were livestock. And the hero trying to empathize with the slave by saying "I totally understand what it feels like" would be laughable if it wasn't so tonedeaf. Imagine saying that you get what a victim of child trafficking went through because your parents grounded you for saying your uncle was making creepy comments. Yea sure, it's bad that happened but holy hell it's not on the same level.
Man, the more I think about this chapter, the worse it gets. I'm glad I dropped this.