Out of curiosity, when did they show that? Every interaction with demons I remember from it they are shown to be manipulating people at best.

The "Diplomatic Envoys" were literally trying to figure out the town's barrier so their master could come in and slaughter them.

The "little girl" in the flashback with Himmel outright says that she called out for her "Mommy" despite demons literally abandoning their young once they're born because "that word stops humans" and nothing more.

Like yeah it's inherently difficult writing something that looks human as actually an irredeemable monster that the only solution is destruction because dehumanizing vulnerable groups is pretty much always the first step in real life genocides. But I don't recall any instances of demons in Frieren actually showing "humanity" for any other reason than to manipulate and kill humans.