I think its kinda bs that he has no problem with killing demons but has a problem with killing humans. Sure he's technically human but he is on the demon side not the human side so he should be more fond of demons than humans in this world.
@Alex-dono-sama
It does make sense though
Whether the general was human or demon, he is someone who kills the weak just because he thinks he is better than them
Killing demons who have no reservations about killing anyone, even their own kind, seems logical