If you're one of those people that despise watching the mc get abused and do absolutely nothing about it, never even get angry, then close the tab quickly. Ain't gunna lie I thought he'd leave the humans that are truly awful and go support the demons. Nope. At the point I read up to this dude should've been collecting heads by now. Every single character the reader meets is worse than the last. Only the demons are even half decent occasionally.
You're acting like this was ever meant to be some deep, fleshed-out story. It's just a horny degenerate bait manga. If you're looking for the sort of story you've described, go read an edgy manga with a violence-obsessed Gary Stu protagonist. That side of the isekai community seems to be what you're looking for.
Don't pretend you didn't know exactly what you were signing up for because the summary and the tags told you everything you'd need to know. Another thing, the demons aren't half decent, not even occasionally. They're senseless murderers who target humans just to kill them. They don’t even care about the protagonist as a person; they’re only interested in the power he can provide. The humans, at the very least, have moral justification for their desire to kill demons.