The Sarge (who I am portraying as a lazy and incompetent Nazi) answers, "Mice! Move on".

The final layer of ignorance in the routine is that, instead of taking the obvious and correct stance that Nazis were disgusting, immoral and evil, I merely conclude that they were "rubbish" because of their inability to find Anne Frank earlier - like it was all part of a big, mutually agreed game of hide-and-seek.
I can see if you took this routine at face value as my real opinion on this profound and heroic tragedy, it could be deemed highly offensive. However, this is obviously an absurd comic position with the audience well in on the joke, fully aware that I am saying the exact opposite of what every right-minded person thinks.
I often get accused of finding comedy in places where no comedy is to be found. I feel you can make a joke about anything. It just depends on what the joke is. Comedy comes from a good or a bad place and the problem is in its interpretation, with some people confusing the subject of a joke with the joke's real target. The target of this joke is the comedian's ignorance.