I have had that routine for nearly 10 years now. It is about the misunderstanding and ignorance of what is clearly a tragic and horrific situation. My comic persona is that of a man who speaks with great arrogance and authority but who along the way reveals his immense stupidity.
In this particular routine, I envisage an almost slapstick version of the Nazis entering the home of Anne Frank on a daily basis and always failing to bother to "look upstairs".
I even have one of them suggest, "Looking upstairs today, Sarge?" The officer replies, "No, let's move on."
The first Nazi then says: "What's that tapping sound?" - as I mime using an old fashioned typewriter. Again the joke here is the supremely stupid assumption that Anne Frank obliviously and noisily typed her diary.