Frieren reminds me of my readings about the 19th century Texas Rangers (see Cult of Glory (2020) by Doug J. Swanson) and how Native Americans were literally seen as vermin to be exterminated, even if they assisted in exterminating other indigenous. In real life, a lack of communication and 15th century epidemics divided indigenous peoples who could have otherwise defended their sovereignty; once indigenous children learned the conquering host people's language (English) and affirmative action applied to close egregious wealth gaps, indigenous people have proved to be ordinary people with another skin color (evidence: me, a member of the Navajo Nation). Frieren, in contrast, portrays a demon child as being irredeemably evil even though they learn the host language and are given second chances and extra attention (by the Himmel); the author implies there is some cognitive divide due to demons being solitary creatures who raise and teach themselves from a very early age (presumably much earlier than the failed experiment Himmel performed); however, that subtlety isn't emphasized and demons are more akin to starfish aliens than people.

Overall, I think provoking controversy and discussion around this point is valuable because it invites people to debate the nature of Otherness. In which ways can a person be different enough before they stop being people? What exactly are the differences between “person” and “beast”? Is focusing on those differences the root cause of genocide? Do we hesitate to relax the requirements to be considered a person because we dislike the economic consequences? (e.g. the horror of teaching factory farmed animals to speak)

I personally consider demons in Frieren analogous to indigenous before colonizing powers, albeit sustained by their long life spans and tendency to independently discover powerful technology (magic). I doubt the author is thinking very hard along these lines, and so fear they will fall back on tried and true story patterns in which animalistic heathens are purged to make way for civilization. But I hope to be surprised.