The problem with the demons in Frieren is that they're incredibly contradictory and badly written. They don't understand human emotions, and yet their entire modus operandi is manipulating people's emotions? They don't have emotions and yet Lugner got mad about Frieren hiding her mana and Aura cried when Frieren forced her to kill herself? They don't have morals, and yet they think hiding your mana is wrong and they think other demons dying is wrong? They're smart enough to engage in political conversations with other races and yet they don't know what a father is? Nothing about them makes any sense.If the whole demon killing thing wasn't being constantly bolstered by retarded fans and insane right wing reactionaries, people would have pointed out how contradictory and retarded the writing of the demons is a long time ago.