In 2016, Jewish critics of then-presidential candidate Donald Trump became targets of online anti-Semitic attacks that often took the form of digital images, frequently featuring a humanoid frog in a Nazi uniform. These images—“memes” in Internet lingo—introduced the public to an underground online subculture of jokey neo-Nazism. Gavriel Rosenfeld explains the subculture’s development and its dangers:

Memes are videos, catchphrases, and images that spread and mutate from user to user through social-networking sites. . . . [A]s transgressive, attention-grabbing clickbait became an easy method of attracting eyeballs, a new phenomenon arose: the more popular the web image, the greater its likelihood of being “Hitlerized”—from memes of [characters from the children’s cartoon] Teletubbies with Hitler mustaches to jokey depictions of the Führer himself. I have called this the “law of ironic Hitlerization,” and it is anything but funny. This smirking irony helped to normalize Hitler and Nazism in certain precincts of the Internet.

The insidiousness of this trend is epitomized by the fate of Pepe the Frog. Created by the artist Matt Furie in 2005, the cartoon character was originally a likeable loser who did whatever he felt like (“Feels good, man!” was his slogan). Eventually Pepe became Hitlerized, at first for laughs, then as a coded message or secret handshake, and eventually as the ubiquitous symbol of the alt-right. Among his subtler uses was the mocking phrase, “Green lives matter.” . . .

The transformation of Pepe the Frog from innocuous Internet icon to de-facto swastika highlights the utility of memes for the alt-right. They are the visual counterparts to the idiosyncratic vocabulary and numerology used by the alt-right—for instance, “cucks” for mainstream conservatives and “1488” to signal the fourteen-word white-power pledge together with the salutation “Heil Hitler” (the eighth letter of the alphabet is h). The ostensible irony of these catchphrases provides extremists with plausible deniability. . . .

[In effect], ironic memes are gateway drugs. Various alt-right activists have reported that they were initially attracted to ironic memes as fun ways to troll liberals, and their prolonged exposure eventually led them to become “red-pilled”—in their parlance, “enlightened”—and embrace more overtly anti-Semitic imagery. This explains why some members of the alt-right eventually migrated from Pepe the Frog to “Le Happy Merchant,” a hooked-nosed Jew rubbing his hands together conspiratorially. The image was seen on the 4chan website as early as 2012 and is arguably the most widely used anti-Semitic meme on the web today.

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.