It's fantasy.

Not every villain needs to have a complex backstory for why they're sympathetic and actually human. Great example: the Disney Cruella remake. The character is more fun as a literal human demon who wants to make a dog skin coat. She doesn't need to be a humanized person.

Obviously when tropes combine (looking at JKR and the goblin bankers) that's a different thing. But the fact that many of the Demons are ATTRACTIVE is part of why we should recognize them as (if anything) analogs to fascists.

To think through this: is it "problematic" that certain creatures in nature use aesthetically pleasing colors to trap prey? Is this somehow something we should "humanize" rather than recognize the cold calculation of nature at work (and perhaps, as communists/marxists, work to fight against the logic of nature and fascism's evil cooption of it. After all, don't we believe that men make history, but not as they please, and thus are beyond mere "nature").

The key difference between the fash cooption and the reality of the story is that the demons are not human. They're angler fish/carnivorous plants that use language. This idiot's take (the OP image) obviously assumes the inhumanity of his subjects and that's all you have to do to undermine every Frieren bad take. Simply put, the real "analogy" is if you went to go make friends with a starving tiger in the wild. It doesn't see its actions as good or bad - it's "beyond" good and evil not because they're niezschean ubermensch but because they're simply nonhuman. Now, this doesn't mean we should kill every nonhuman entity in the world (though cattle ranchers would do so with wolves, evil fucks). We can recognize ecosystems and our role in it. But it's a fantasy story, and should be taken on its own terms until it gives reason not to (and again, if every demon started looking like a JKR goblin or something, then I would immediately reverse my position).

Frieren does traffic so heavily in fascist tropes

It quite literally does the exact opposite, repeatedly and emphatically devaluing everything Fascists value and making its villains just do literally every Fascist thing. Its only misstep is in making a species of ontologically-fascist demons who just can't help but do fascist things. If Frieren were fascist it would be oriented around fascist ideals instead of just stumbling into a problematic analogue to one facet of real-world fascist propaganda by making its might-makes-right, anti-empathic, elitist, warrior-cult, racial-supremacist villains innately fascist by dint of being magical predators, instead of making them simply indoctrinated into that ethos or the like.

This is even more tiring than the Dandadan struggle sessions.