Imagine going for a night out to the theatre in Germany during the 1930s. It would have been quite normal – with not one eyebrow raised in the audience – to be watching a production which showed film footage of Jews being beaten up. This would not be shown to elicit any sympathy, but purely to work up the crowd’s bilious hatred even more. Then a short while later in the same production the clever actors would prompt the audience to start singing songs that encouraged even more visceral hatred for the Jews. Lyrics such as “Those Jews are all...