My first objection to Frieren is that it is patently uninterested in what demons are. It is a question that is only given enough time to (badly) justify violence. On the other hand, Frieren dwells for a very long time on the (taken-for-granted) "fact" that the only valid response to their existence is killing them mercilessly.
It pulls a bunch of half-justifications for this out of its ass. One second they're robotic beings that feel nothing (except we are, as an audience, clearly shown a survival instinct, which is a feeling), the next it is because they are sociopaths (which is something else), except specifically to a degree that simultaneously allows them to form societies and raise armies but not enough for coexistence with humans to ever be possible. What a philosophically rich claim to make! A good writer could become the next Locke, Hobbes or Marx just exploring that!
Neither option is explored at all. Again, good art has been made discussing topics like this. Do Androids Dream of Electric Sheep? comes to mind. That's a complex exploration of whether unfeeling automata can function in society. Frieren isn't. Frieren takes for granted that whatever demon lore is true this second is sufficient justification for violence, because that's the solution Frieren wants. This show threw a half-baked concept in because they wanted a scene where Frieren and Fern mow down hordes of bad guys. The monstrous political implications are just a clumsy byproduct of unexamined authorial bias.
And when I'm at it, the first demon looks cool as hell and then every subsequent demon looks like an Anne Rice vampire. That's lame!
Also the rest of the show is just crap, as well. The world is a generic Japanese DnD setting without a single element that required more than a few seconds and a German dictionary to come up with. The plot starts off pretending to be "deep" by going through the motions of a lousy Oscarbait drama for a few episodes and then becomes aimless weebslop for fifteen episodes or so. Characters are introduced and thrown away randomly as the writers appear to try to chart the path of the show based on live audience feedback, and then the disgustingly long examination arc begins, and I really would like to hear a fan justify that.
What is that giant waste of everyone's time for? Firstly, it makes Frieren's barebones worldbuilding take center stage ("Your next task is to 'clear a dungeon' because this entire show takes place in a role-playing game!"), secondly it makes some of the most unappealing and jarring character introductions I have ever seen, ("You know what this high fantasy setting needs? Asuka Langley Soryu, but with green hair and she's dressed like a mall goth in a black open back minidress! Oh, but here's the twist! Remember how Asuka is an arrogant twerp because she is a deeply insecure, traumatized little girl in constant need of external validation? What if this Asuka is exactly the hot shit she thinks she is?").
Third, and worst, is that this show just decides that human life isn't worth anything once this arc begins.
One full third of season one is taken up by the main characters going to the Magic DMV. One-Punch Man was mocking this stupid, overdone anime trope in 2009.
Of course, the Magic DMV has a Tryhard Worthiness Test. They do hunger games shit. They also don't test people's magic ability even once. I'm pretty sure Stark (who does not have magic) could pass every trial in the Magic DMV's Tryhard Worthiness Test if he put his mind to it.
People die left and right at the Magic DMV. Some Bushido Dipshit makes a pithy remark about this being fine; they were Unworthy, after all. I want Frieren's fans to explain to me how this develops on the themes this show is allegedly about.
Why are they going to the Magic DMV? Because no one in the northern region (creatively named "The Northern Region") can travel without a Magic Driver's License. Canonically, in this world, a test that passes single-digit numbers of people every three years is the only way to be allowed to travel. This raises interesting questions like, "Is there commerce here, like, at all?" and, "Do the writers think I'm a moron?" If only a few dozen living people have a Magic Driver's License, there's literally not enough people who can freely travel to hire anyone to enforce the rule to begin with!
Enough about the Magic DMV. It is so infuriatingly stupid (and boring) that I could talk about it all day, but I need to circle back to my main point.
People misreading the demons as saying Something Deep is dumb as hell (apply the handy Adam Test if you want; I just made it up: "Does the show dwell on it?" It also comes with the attached maxim: "Fiction is about what it dwells on." Shockingly deep insight, I know, but I've been in college writing classes where people insist a book is mainly "about" something that is only mentioned in one chapter.) Do you know what's dumber than the allegations of fascism, though? The allegations of good writing. This entire show is a paint-by-numbers pastiche of bad taste and bad art. Not only is it bad, it is informed by, and strives to imitate, other art that is also bad. It is four or five degrees removed from anything you could consider good, or even trying to be good.
I wouldn't recommend this show to my worst enemy.