Criticizing Israel doesn’t make you anti-Semitic: If it’s been said once, it’s been said a thousand times. Yet somehow that message doesn’t seem to have reached the hundreds of anti-Israel demonstrators in Fort Lauderdale, Fla., who turned out last week to protest Israel’s military operation in Gaza. As their signs and chants made clear, it isn’t only the Jewish state’s policies they oppose. Their animus goes further.

Demonstrators chanted “Nuke, nuke Israel!” and carried placards accusing Israel of “ethnic cleansing” and bearing such messages as: “Did Israel take notes during the Holocaust? Happy Hanukkah.” To the dozen or so supporters of Israel gathered across the street, one demonstrator shouted: “Murderers! Go back to the ovens! You need a big oven.”

The Arab-Israeli conflict induces strong passions, and the line that separates legitimate disapproval of Israel from anti-Semitism may not always be obvious. But it’s safe to assume the line has been crossed when you hear someone urging Jews “back to the ovens.”

The Danish website Snaphanen posted a photo the other day of a pamphlet being distributed in Copenhagen’s City Hall Square. On one side it proclaimed: “Never Peace With Israel!” and “Kill Israel’s People!” On the other side: “Kill Jewish people evry where in ther world!” The leaflet’s spelling left something to be desired, but its message of genocidal anti-Semitism couldn’t have been clearer.

Likewise the message in Amsterdam on Saturday, where the crowd at an anti-Israel rally repeatedly chanted, “Hamas! Hamas! Jews to the gas.” And the message in Belgium, where pro-Hamas demonstrators torched Israeli flags, burned a public menorah, and painted swastikas on Jewish-owned shops.

Only marginally less vile is the message that has been trumpeted at demonstrations from Boston to Los Angeles to Vancouver: “Palestine will be free/ From the river to the sea” - a restatement in rhyme of Mahmoud Ahmadinejad’s call for Israel to be “wiped from the map.”

Let’s say it for the thousand-and-first time: Every negative comment about Israel is not an expression of bigotry. Israel is no more immune to criticism than any other country. But it takes willful blindness not to see that anti-Zionism today - opposition to the existence of Israel, rejection of the idea that the Jewish people are entitled to a state - is merely the old wine of anti-Semitism in its newest bottle.

The hatred of Jews has always been protean, readily revising itself to reflect the idiom of its age. At times, it targeted Jews for their religion, demonizing them as Christ-killers or enemies of the true faith. At other times, Jews have been damned as disloyal fifth columns to be suppressed or expelled, or as a racial malignancy to be physically exterminated.

In our day, Jew-hatred expresses itself overwhelmingly in national terms: It is the Jewish state that the haters are obsessed with. “What anti-Semitism once did to Jews as people, it now does to Jews as a people,” the British commentator Melanie Phillips has written. “First it wanted the Jewish religion, and then the Jews themselves, to disappear; now it wants the Jewish state to disappear.”

The claim that anti-Zionism isn’t bigotry would be preposterous in any other context. Imagine someone vehemently asserting that Ireland has no right to exist, that Irish nationalism is racism, and that those who murder Irishmen are actually victims deserving the world’s sympathy. Who would take his fulminations for anything but anti-Irish bigotry? Or believe him if he said that he harbors no prejudice against the Irish?

By the same token, those who demonize and delegitimize Israel, who say the world would be better off without it, who hold it to standards of perfection no other country is held to, who extol or commiserate with its mortal enemies, who liken it to Nazi Germany and apartheid South Africa, who make it the scapegoat not only for crimes it hasn’t committed, but for those of which it is a victim - yes, such people are anti-Semitic, whether they acknowledge it or not.

Criticize Israel? Certainly. But those who so loudly denounce Israel in its war against Hamas are siding with some of the most virulent Jew-haters on earth. They may tell themselves that that doesn’t make them anti-Semites. But it does. “When people criticize Zionists,” Martin Luther King said in 1968, “they mean Jews. You are talking anti-Semitism.”