The accusation that Jews murder Christian children for ritual purposes can be traced back to Roman times, but the form of the libel that has persisted to this day first emerged in 12th-century England, when the death of young William of Norwich was blamed on local Jews. In a recent book on the subject, E. M. Rose argues that the accusation tended to originate with individuals who had a vested personal interest (usually in the form of large debts owed to Jewish moneylenders) in the outcome. In a review, Madeleine Schwartz questions the underlying thesis:

[Rose] makes it clear that the blood-libel story didn’t emerge from an untapped well of hate. “This supposed ‘irrational,’ ‘bizarre,’ ‘literary trope’ was the product of lucid, cogent arguments, thoughtfully and carefully debated in executive councils, judged in detail by sober men who were not reacting under pressure to thoughtless mob violence,” she writes. She argues that the blood libel was an accusation developed by rational men in need of a “strategy”—a word Rose uses repeatedly throughout her book.

She shows how slowly the blood libel spread and takes this as an indication that the myth’s anti-Semitic sentiments were not easily accepted. [The clergyman Thomas of Monmouth’s] account of William’s death, for example, contains repeated defenses of [William’s] holiness, as if the monk is constantly imagining the retorts of naysayers who don’t believe the young man should become a saint. . . . The extortion of Jews in Gloucester using the blood libel happened two decades after William of Norwich’s death; it wasn’t until 1168—more than twenty years after the initial charge was made—that the blood libel began to gain ground in Europe. . . .

Rose stops short of showing why the blood libel persisted, consistent in form, for centuries after its first dissemination. In her emphasis on the rational reasons for the story’s initial diffusion, she downplays the enduring, and less rational, religious stories it might well have echoed among the people who heard it. Yet once it gained initial acceptance, the accusation of ritual murder was easily believed by men and women far removed from . . . any of the tangible, tactical reasons for its spread.

Why did they find this charge credible? One story that would have been familiar to them is the account of Christ’s Passion and suffering at the hands of the Jews. It’s not hard to imagine that the popularity and tenacity of the blood libel rests in part on how deftly it reimagines that story.

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.