I genuinely want to know what happened to him to make him like this. I remember reading somewhere that he was severely bullied growing up, and given with how AoT is now just one big racist, nihilistic, misanthropic, edgelord revenge fic, I can believe that. You know, if that is the case, and if Isayama is a literal autist like he seems to be, everything in AoT kinda makes a bit more sense.
Not storywise, or in-story really, mind you, but meta-wise. It explains why everyone hates the Eldians because like you said, Isayama might actually be incapable of understanding that people have different points of view and that the vast majority of people aren't hateful, angry speds like he is.
It's actually kind of sad, really. AoT might've just turned into the rambling, racist, misanthropic, sadistic, illogical, nihilistic, edgelord revenge fantasy fanfic of a man who wishes to get back the world for things that don't even matter anymore.