During Bill de Blasio’s tenure, New York City has seen attacks on visibly Orthodox Jews become a near-daily occurrence that the mayor has had little success in curbing. One reason for this failure, argue Philip Klein and Seth Mandel, is his stubborn conviction that, as he put it in a speech last year, “the ideological movement that is anti-Semitic is the right-wing movement.”

De Blasio’s failed leadership is an example of the real-world danger of trying to explain anti-Semitism as merely the [product] of one side of the political spectrum. By narrowly defining anti-Semitism as a far-right problem that has suddenly bubbled up under President Trump, liberals and their allies in the media are not only spreading misinformation but are making it more difficult to address a complex and growing crisis seriously. Failing to understand that anti-Semitism comes in many forms is one reason why rising violence against Jews has been able to fester and grow.

Unfortunately, de Blasio’s effort to explain anti-Semitism as merely right-wing does not make him unique. As anti-Semitism has reared its ugly head, liberals have gone out of their way to categorize it in a way that fits neatly with their partisan interests.

Senator Bernie Sanders, whose campaign has provided a safe haven to anti-Semites of the left, argued that the spike in anti-Semitic attacks nationwide was “a result of a dangerous political ideology that targets Jews and anyone who does not fit a narrow vision of a whites-only America.” One of Sanders’s prized endorsements came from Representative Ilhan Omar, who has brought anti-Semitic conspiracies about all-powerful Jewish puppet masters to the halls of Congress.

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.