Sceptical readers of Shindler's book might go further and wonder what his history of left-wing anti-Semitism has to do with them. By "the Left" he means the far Left. In Stalin and Mao's day it was one of the most horrifying forces humanity has witnessed. Now it is nothing. The Soviet Union is gone. China is a state capitalist power. Who cares about Communism? It is as dead as the Albigensian heresy or the Stuart claim to the English throne. Even Marxists don't believe in Marxist-Leninism any more.

But in a strange manner few discuss, the death of Communism has freed far-Left ideas from the cage of the Cold War. When the far Left was a global force, the mainstream liberal Left had to draw dividing lines and defend itself from its attacks. Now that the far Left threatens no one, the borders have gone. The media would hound from public life any conservative who shared platforms with members of a neo-Nazi group. But respectable leftists can now associate with those who would once have been regarded as poisonous extremists — and no one notices. What applies to personal alliances applies equally to ideology. Foul ideas flood past the unmanned border posts, with disastrous consequences for Jews and Arabs.

The influence of far-Left ideas on attitudes towards the Israeli/Palestinian conflict is too obvious to spend much time on. You will have noticed how rarely discussion of a workable solution appears. Most Israelis and most Palestinians favour a compromise, which includes a fair distribution of land, an end to violence, and security — essentially dividing the country on 1967 lines. Compromise is as much an anathema to the far Left and the Islamists as it is to the Israeli and American Right. Increasingly, it is anathema to the mainstream liberal Left as well. The notion that Israel is an illegitimate state has gone from the fringe to the mainstream of left-wing discourse.

For Arabs, the European Left is proving a disastrous influence. The spirit of the Hitler-Stalin pact lives on in the coalition between white leftists and the Islamist religious Right. Such alliances are scandalous. They can bring no good to Arabs in general and Arab women in particular. They expose the insincerity of the anti-sexist and anti-racist principles that leftists claim to hold. Yet they are tolerated almost without comment. Islamists are against the West in general and Israel in particular, and the Left can ignore the sufferings that theocrats impose from Iran to Gaza. This tendency to forget about the very people you say you are championing is the final legacy of a dark past.