Reflecting on the British Labor party’s selection of Jeremy Corbyn—who praises Hamas and Hizballah, and peddles 9/11 conspiracy theories on Iranian state television—as its new leader, David Hirsh examines the rise of a form of anti-Jewish politics that is at once new and, often, very old:

The intense personal payoff of this variant of identity politics is a feeling of inner cleanliness. The world may be utterly compromised and there may be nothing I can do about it, but it isn’t going to be my fault, my own soul is clean. . . .

It is not accidental that . . . anti-Semitism has become pivotal to this process of defining who is inside and who is not. In the postwar period, in democratic discourse at least, everybody recognized anti-Semitism as being bad and they recognized opposition to anti-Semitism as an entry requirement into progressive politics. Now, just the action of initiating a discussion about what is anti-Semitic and what is not rings alarm bells for people schooled in progressive culture. To ask if something said or done is anti-Semitic, if it relates to Israel or Palestinians, is to risk placing one’s own membership of the community of the good under scrutiny. . . .

Moreover, there is a wider context: a deep reservoir of anti-Semitic discourse, images, emotions, and tropes within . . . Western culture. [This reservoir] has been deposited by the distinct waves of anti-Semitism that have washed over Europe since the original rise of Christianity out of Judaism. It would be surprising indeed if a campaign to make people think of Israelis as being outside of the community of the civilized did not draw, even unconsciously, on these ready-made ways of thinking, linked to intense affective triggers.

The campaign to treat Israelis and their “supporters” as pariahs tends to bring with it echoes of previous campaigns against Jews. Images and tropes from old anti-Semitic themes are unconsciously recycled, and Jews who oppose the boycott [of Israel] are framed as conspiratorial, powerful, rich, bloodthirsty (particularly for children’s blood), bourgeois, connected to dishonest bankers, warmongers, etc.

Two extraordinary events demonstrate something important about Israel’s most fervent adversaries. One was a speech given at something called The People’s Forum (funded generously by Goldman Sachs), which stated, “When the state of Israel is finally destroyed and erased from history, that will be the single most important blow we can give to destroying capitalism and imperialism.”

The suggestion that this tiny state is the linchpin of a global, centuries-old phenomenon like capitalism goes well beyond anything resembling rational criticism. Even if Israel were guilty of genocide, apartheid, and oppression—which of course it is not—it would not follow that its destruction would help end capitalism or imperialism.

The other was an anti-Israel protest that took place in front of New York City’s Memorial Sloan Kettering Cancer Center, deemed “complicit” in Israel’s evils. At organizers’ urging, participants shouted their slogans at kids in the cancer ward, who were watching from the windows. Given Hamas’s indifference toward the lives of Gazan children, such callousness toward non-Palestinian children from Hamas’s Western allies shouldn’t be surprising. The protest—like the abovementioned speech—deliberately conveyed the message that Israel is the ultimate evil and its destruction the ultimate good, cancer patients be damned.

The fact that Israel’s adversaries are almost comically perverse does not mean that they can be dismissed. If its allies fail to understand the obsessive and irrational hatred that it faces, they cannot effectively help it defend itself.