Leftists have long had a blind spot when it comes to antisemitism. This is partly because some have found comfort in this rank bigotry, seeing Jews as a privileged elite and a personification of the capitalism they abhor. But it is also because they like to define antisemitism on their own terms, showing disdain for how Jews themselves feel.

They recognise and condemn its more usual manifestations, particularly when it comes packaged with swastikas, jackboots and lethal rhetoric. But they refuse to recognise the other side of Jew baiting -- the double standards, the conspiracy thinking, the Holocaust inversion and the anti-Zionism.

Owen Jones clearly has the blind spot just mentioned. In an article in Monday's Guardian, Jones discusses the menace of antisemitism in Europe. He recognises that it has spiked during the conflict in Gaza and argues that 'attempts to belittle it are dangerous, allowing the tumour to spread unchecked'.

He dismisses those who try to deflect blame onto the Jews themselves. This, he says, is like 'rationalising anti-Muslim prejudice as the inevitable consequence of Islamist fundamentalist terror'. So far, so good.

But then he gets unstuck. First, he raises the old canard that pro-Israel supporters accuse 'pro-Palestinian' protestors of being antisemitic in an attempt to silence criticism of Israel.

The danger is that the 'meaning of antisemitism is lost, making it all the more difficult to identify and eliminate hatred against Jewish people at a time when it is rising'. He goes on to say that for some defenders of Israel’s governments, the 'supposed special attention received by the conflict is itself evidence of antisemitism'.

In reality, he argues that these protestors are condemning the actions of a heavily armed state backed by the West.

The idea that Israel's supporters routinely accuse their critics of antisemitism is essentially fictitious. The vast majority of these supporters can recognise the difference between criticism of Israeli policy and baseless hatred. Virtually no sane Zionist sympathiser would label someone antisemitic simply for criticising policy on the West Bank or settlements. These are matters of legitimate public discourse.

But what these supporters will argue, justifiably, is that the discourse on the conflict has become badly corrupted. Israel has been likened to a Nazi state that is engaged in a policy of wholesale extermination. Only recently, Lord Prescott labelled Gaza a 'concentration camp' in an article for the Mirror. Others, like David Ward and Lee Jasper, have used Holocaust Memorial Day to attack Israel and the Jews.

Cartoonists have routinely tapped into antisemitic stereotypes to depict Israeli leaders, the most popular of which evoke images of the blood libel. The 'all powerful' Israel lobby is accused of being an evil puppet master, manipulating western foreign policy for its own insidious ends. This taps into a centuries old stereotype of sinister and demonic Jews controlling the world.

Supporters of Israel have every reason to condemn such ugly displays of bigotry. Yet the accusation is trotted out that they accuse every critic of anti semitism, which is absurd. This is an attempt to silence and smear Zionists, not critics of Israel. Maybe Owen Jones should answer this question: How nasty must criticism of Israel become before it can be considered antisemitic, or at least bigoted?

Is it acceptable to portray Netanyahu as a hook nosed Jew revelling in Palestinian blood, as a latter day satanic Hitler or perhaps as an evil puppet master controlling western leaders? Unfortunately, images such as these have proliferated at anti-Israeli rallies around the world.

Jones is anxious to defend those who go on 'pro-Palestinian' rallies. But the unmistakeable sentiment from marchers is unmitigated hostility to Zionism and a Palestine free 'from the river to the sea'. Yet Zionism is simply the acknowledgement that the Jews are a nation with a collective right to self-determination.

Anti-Zionists deny Jews this right while granting it to every other nation. That is why true progressives, like the great Martin Luther King, have long recognised the connection between hostility to Zionism and hostility to Jews.

Jones secondly fails to understand how antisemitism is often dressed up in 'progressive' form. He (rightly) mentions the danger from Front National, Jobbik and Golden Dawn, three extreme groups suffused with xenophobic prejudice against Jews, immigrants and Muslims. He condemns attacks on synagogues in Paris as well as other assaults.

But antisemitism is not just about jackboots and swastikas, torched synagogues and racist insults. It is about discriminating unfairly against Jews, Jewish institutions and Israelis.

It is about holding Jews to a different standard or demanding from them a unique level of behaviour. It is about calculated offence, such as abusing the memory of the Holocaust for political ends. Nor does antisemitism have to be intended for it to be real.

When we stop viewing this prejudice through far right tinted spectacles, we can understand why Kilburn's Tricycle theatre has been accused of racism. Last week, the Tricycle boycotted the UK Jewish Film Festival after the latter refused to accept a condition that it first reject £1,400 of funding from the Israeli embassy.

The Tricycle suggested that UKJFF was being politicised by this money and, by implication, the theatre would be taking sides over the Gaza conflict.

Yet this condition has not been imposed in other cases where cultural institutions have received government funding. To take one example, the Tricycle hosted the London Asian Film Festival, even though it was financed by the Indian government, a party to the long running conflict over Kashmir.

Moreover, the Tricycle has happily taken a sizeable grant from the Arts Council, a government funded body. Yet British governments have recently been mired in controversial wars in Iraq and Afghanistan.

This is a blatant case of an egregious double standard applied to a Jewish cultural group. They, and only they, have been forced to sign up to a political credo (i.e. to dissociate from Israel) before they are deemed 'acceptable'. In an attempt to appear self-righteous, the Tricycle's organisers have engaged in a most pernicious form of bullying.

Had he cast his net further, Jones might have condemned George Galloway after his recent statement that no Israeli tourists were welcome in Bradford.

Galloway was saying that a boycott of Israeli goods and services was not enough; not one Israeli was welcome to step foot in his constituency either. By demanding that Bradford become Israelfrei, Galloway was not engaging in political debate. He was demonising an entire nation.

Equally bigoted was the decision of the Edinburgh Festival to axe 'The City', a play staged by Jerusalem's Incubator Theatre. There were calls for its artists to publicly dissociate themselves from Israel's policies in Gaza and the West Bank before being allowed to perform.

But again, such draconian demands have not been imposed on other nationalities. No other performers have been asked to pass a 'values test' before they can appear, nor should they be. Such behaviour is an outrageous affront to the principle of artistic freedom.

All three examples revolve around Israel and its conflict in Gaza. But Israel is the 'Jew among nations' and the country deserves equal treatment in the court of international opinion. Singling her out unfairly demands some form of explanation.

The motive for doing so is not always racist. Anti-Americanism and hostility to western power galvanise the left, and Israel is a bastion of democratic, western values as well as a staunch ally of America. It is also perceived, wrongly, to be a colonialist power. Hence it is a target of leftist discontent with western power. But the effect of such irrational discrimination and disproportionate focus is no less hurtful than a verbal insult.

It is still targeting the Jews.

It is only when we understand the many ways in which antisemitism manifests itself that we can start tackling it properly. It must be confronted warts and all, and with the blinkers and blind spots removed.

Jeremy Havardi is a journalist and the author of two books, Falling to Pieces, and The Greatest Briton