Incidentally, I'm just as interested whether the quotation is real or allied propaganda - if it's real because of what it says about extreme racist and nationalist movements and what is acceptable to them and because if it's propaganda it's been incredibly effective to have survived this long!

I can think of two other related sorts of thing: The first is Cat's Eyes Cunningham. He was a successful night fighter pilot in WW2 making use of an ultra top secret weapon - radar that fit in a plane. They didn't want to admit they were using radar so they put out the story that he ate a diet rich in carrots because carotene improved his night vision. Pure invention to hide radar, but the idea that carrots improve your night sight is still around .

The other is why Tanks are called Tanks, when they were originally called Landships. Apparently what happened is they need a cover story for what these - again - ultra top secret weapons being transported across countries on trains actually were. The story they came up with is that they were mobile water tanks...