I agree that there's a grey morality with his revenge but i feel like i agree with him, yeah not all of them are bad but their entire race is a dangerous hazard to the world and the other species, they are straight up using the power from an upper living form of life to subjugate the other races only to survive themselves, obviously the protagonist will choose his race as well as the demons will choose theirs, they were lucky that they were stronger but fate gave now humans a weapon in the form of a human inside a demon's body so now they have to suck it up for all they've done, everyone's action has a repercussion and this is theirs