The somewhat reluctant political consensus seems to have concluded that while Jeremy Corbyn’s leadership of the Labour Party has played a central role in the explosion of anti-Semitic abuse that has increased within his party, the Labour leader himself (probably) doesn’t harbour any personal animosity towards the Jewish people.

But it would be a mistake simply to register the increase in anti-Semitism within Labour’s ranks, to note Corbyn’s belated commitment to doing something about it, and then move on to the next political story.

Why on earth is anti-Semitism even a problem within a party that was, until recently, a mainstream, centre left social democratic movement in which anti-Jewish prejudices...