Catherine:

Today I believe that those Auschwitz documentaries were a formative moment in my childhood. Very probably, they were a mild & unrecognized trauma.

Catherine, that’s what monster stories are for. Later you can say “ah, but there aren’t really monsters” but you still have that gut-level wariness when things get spooky. Probably useful on dark city streets, unfamiliar hiking paths, etc.

IMHO, letting kids know the monsters can be real, and can be human, isn’t a bad thing. Harsh, but not bad.