So Wemi is asking why people freak out over Frieren, and it's because of their ideology. They cannot accept that demons are inherently evil because they reject the idea of biological determinism. If they accept that demons are evil and violent, they would see it as an admission that different groups of people are different.
The whole thing is about the blank slate theory. Every person is capable of being a good person. This is why the meme about migrants all being doctors and engineers is a thing. They believe that society is the reason why people rape and murder. If some people are more prone to violence based on genetics, that means the evil White racists win.