In a post about Downfall parodies, Justin has reminded me about the scene in the film where Magda Goebbels murders her six children.
I've watched that film probably half-a-dozen times on Film Four, and it's pretty grim throughout, but I always have to leave the room when that scene comes on. It's spectacularly horrible even in the context of the rest of it all, and I found that when I watched it the first time, I couldn't think of anything else for days afterwards. That, and the line Goebbels gives to one of the bunker's staff on his way out: "The game is up."
The thought that the whole thing could have been - at least in part - a gambit - is almost more chilling than the idea that a group of people could attempt to do what the Nazis did in the conviction that they would succeed.
Even thinking about it is like hearing 'Careless Whisper' on the radio - once it's in your head, there's almost nothing to can do to get it out.