I think that could be more counted as a silly prank. A more strange and much graver case I read of long ago was that of a female Jewish Gestapo officer who hunted Jews in Nazi Germany (sorry, don't remember any details).

But either way, one shouldn't be that surprised: that generalising about groups of people (groups which can't even be properly defined) is false also means that prejudices aren't uniform either, so there may be prejudiced people some of the other prejudiced include in the Evil Group while they themselves don't.

_{*Lunatic*, n.
One whose delusions are out of fashion.}