It all depends on how you define and categorize morality.

The Tolkien dilemma reasoned that since orcs could talk and demonstratively discuss the ideas of right and wrong, then they have some sense of morality. If they have reason and morals, could they at some point decide to stop being evil? And if so, is it moral to eradicate them entirely?

I haven’t read the Frieren manga, but the show referred to its world’s demons as not actually speaking, but having learned to make human-like noises to elicit desired responses. I’m not sure if I buy that explanation (given how the characters behave and converse) but if you do, it’s a functional hedge against feeling bad about our beloved protagonist doing a genocide.

Again, the manga might get into this more. Also this could be a potential character arc for Frieren; whoop lol maybe I shouldn’t do a genocide after all. I do hope it goes this way, but I doubt it will.