A sweet little granny was sitting next to me, knitting a scarf. She was listening to an elderly professor as he delivered a speech about the Holocaust. Every now and then, at the most rousing moments, this tiny old woman would mutter her agreement. "Kikes," she said absently as she nodded her head. "Dirty fucking kikes." Nobody objected; nobody even turned to look. This Nazi granny was among friends.
I was sitting in a bland hotel in Orange County, California - one of those interchangeable global hotels that could be anywhere, or nowhere - at the 2003 conference of the "Institute for Historical Review". It's an outfit of maniacs who claim the Holocaust is at best exaggerated, at worst a fabrication. Robert Faurisson, a disgraced former Professor of Literature at the University of Lyons, represented the conference's liberal wing: in his speech, he admitted that "the Jews were persecuted" but quickly added "they were protected by Hitler too". Some grumbled - why was he so soft?
That conference has been coming back to me in Nam-style flashbacks over the past month. Once you have been in an immersion tank of pure Jew-hatred, it's easier to spot its diluted flavour elsewhere. I hear it now mostly not from the Faurissons and Mel Gibsons but from people who consider themselves liberal and anti-racist.
While Israel was bombing Lebanon in its obscene, pointless war, the priority was to condemn it. Now the Lebanese war is finally stammering to an end - although the crimes against humanity in Gaza and the West Bank continue - we need to talk about the fact that streaks of raw Jew-hatred have re-entered our public discourse. On the 350th anniversary of the glorious return of Jews to England, we are celebrating with an upsurge of spite. It is those of us who are very critical of Israel who must guard most vehemently against this impostor.
Sometimes it emerges in small, unconscious ways. While I was having a haircut last week, my hairdresser got talking to me about the Middle East meltdown because he knows I have spent time out in the trashed, smashed refugee camps of Gaza. "Is it true that whenever George Bush makes decisions on the Middle East, it is because a group of rabbis have been called in and he does everything they say because he has to?" In his gabbled follow-up, he said, "the Jews control Bush" more than once. His scissors were very close to my throat, so I asked where he had heard this. "From a mate," he said.
I would have been astonished if he had made racist statements about black or Asian people; but the most surprising thing about this little encounter is that I wasn't surprised at all. Comments like this are now circling the mainstream; I hear them at parties and on the Tube. He really didn't know the intellectual antecedents for the idea of a secret Jewish cabal pulling the strings of the powerful. (The idea is strangely elastic: the Jews have now been responsible for capitalism, Bolshevism, 9/11 and neoconservatism).
Sometimes it is more blatant. Here at the Edinburgh Festival - as Jamie Glassman, one of the writers for the Ali G Show, has pointed out - there has been a fever of nakedly anti-Semitic jokes. The Australian comedian Steve Hughes declared on stage that he wanted to "kill that fucking Jew Richard Perle", and suggested teaching kids to play Nazis and Jews rather than that other genocide-themed game, Cowboys and Indians. This prompted an audience member to hilariously yell out "Throw them in the ovens", to much laughter. Reginald D Hunter has bragged on stage that he wants to go to Austria and deny the Holocaust so he can be arrested - only to declare at his trial that he was denying the Rwandan holocaust, not the Jewish one. Ho ho.
Some people seem to think that because Jews are generally wealthier than other ethnic minorities, they are protected from the consequences of racist statements like this. Well, tell that to the 48 Jews attacked by racist thugs in Britain this April alone, or to the security guards that now need to search everyone as they enter a synagogue for weapons or suicide-packs.
So where is the boundary between necessary criticism of Israel - or indeed the Jewish religion, which like all monotheisms is based on a ridiculous and often ugly pre-modern text - and racism? It's easy to identify the extremes, the Hugheses or Gibsons, but harder to see the shades of grey building towards them, partly because anti-Semitism is a concept that has been more abused than Tina Turner at the hands of Ike.
From the right, the Israel-right-or-wrong brigade label every critic of Israel a Jew-hater. Melanie Phillips takes the widespread criticism of Israel's carnage in Lebanon as evidence that Britain is now "like Weimar Germany". From the left, some people refuse to see anti-Semitism even when it is pogromming in their face. The Socialist Workers Party, for example, has paraded Gilad Atzmon at their conferences, a man who says it is "irrelevant" whether the Protocols of the Elders of Zion are a forgery because "American Jews do try to control the world by proxy".
But these Siamese delusions are no excuse for rational people to refuse to see the truth. The line between criticism and racism lies with one, unspoken idea: that there is an underlying Jewish essence that can be distilled and condemned. Anti-Semites invariably believe "the Jews" stand for one thing, whether it is communism or Christ-killing (step forward, Mel) or hyper-Zionism. This is absurd when applied to any ethnic group, but particularly foolish when applied to Jews, one of the most fissiparous groups ever to huddle together under one tribal label. After the fall of the Taliban, the two remaining Afghan Jews were found guarding a synagogue - and they were eager to tell bemused journalists why the other Jew was a traitor and a pig. It was a living illustration of the old quip that where you have two Jews you have three factions.
Does anybody really think a tribe that includes Ariel Sharon and Noam Chomsky, Leon Trotsky and the Rothschilds, Mel Brooks and Mel Phillips, has a shared essence? Of course it is reasonable to condemn the views of some Jews, some of the time. But at every stage you must point out that there are other Jews holding precisely the opposite opinions. Those who condemn "the Jews" for what they do or think are chasing a yellow-starred will o' the wisp; there is nothing there except a quaint tribal identification that would probably have melted away long ago without the constant opposition of Jew-haters. Anti-Semitism used to be called "the socialism of fools". Today, it is the radicalism of morons.