@anhedonia @TeaTootler
I must admit I have not met the "don't kill them or you will become just like them" trope yet. To me it sounds like the typical Japanese thing to purify the evil instead of killing the one possessed by it. This has roots in Japanese religion.

In this sense I can see how Frieren departs from this tradition by outright stating she wants to kill Demons.

But does it really depart from this tradition? If we see the Demons in Frieren as physical manifestations of evil, then they cannot be purified. If they cannot be purified, then they have to be removed. Perhaps it's not Frieren the character that departs from the tradition, but the worldbuilding by clearly presenting a race as irredeemably evil.

A connection to Nazis? I don't see it. Nazis clearly saw the Jewish element in Germany as a threat to Germany's existence, therefore seeking for ways to expel it out of Germany. With that being said, there were plenty of Jews working with and as Nazis, showing that there is no correlation between Jews in Nazi Germany, and Demons in Frieren. This connection is based on wishful thinking and careless reading of both situations.