Israel's justified, in fact long delayed, military response to the rocket fire from Gaza triggered debate worldwide. Some criticism was reasonable, anguished, sympathizing with a state's right to self-defense after eight years of bombardment, no matter how intermittent, while questioning the response's intensity. Alas, much criticism was - dare we say it - disproportionate, dishonest and frequently discriminatory. Shouting at Jews "go back to your ovens" in Fort Lauderdale, vandalizing synagogues in Chicago, smashing Starbucks Coffee windows in London, lacks any ambiguity. The barrage of criticism launched illustrates how quickly condemnation of Israeli actions degenerates into anti-Zionism, which is often a thin veneer for anti-Semitism. Although calling the response disproportionate implicitly conceded that some response was justified, most critics went further. Critics silent about Muslim murders of fellow Muslims in Gaza, Iraq or Sudan became obsessed with Israel's "crimes," no matter how surgical the IDF tried to be. More disturbing, the Mideast conflict's dysfunctional, polarizing gravitational physics led many who criticized Israel's actions to idealize Hamas. Demonstrating this dishonesty in prominent essays in The Washington Post, Guardian and The New York Times, respectively, former president Jimmy Carter, Avi Shlaim of Oxford University and Rashid Khalidi of Columbia University all sanitized Hamas to demonize Israel. Carter treated Hamas as a peace-loving movement seeking a "comprehensive cease-fire in both the West Bank and Gaza," ignoring its charter's vows to destroy Israel. Khalidi defined Israel's 2009 war aims by unearthing a 2002 comment from Moshe Ya'alon, chief of General Staff at the time, about trying to crush Palestinians, ignoring many more recent, far uglier, Palestinian calls to annihilate Israel. And in a down-is-up essay, wherein Israel's painful withdrawal from Gaza became an attempt to expand its territory, Shlaim treated Hamas as a democratic movement even though it seized power in a coup by murdering fellow Palestinians. Shaim wrote of Hamas: "Denied the fruit of its electoral victory and confronted with an unscrupulous adversary, it has resorted to the weapon of the weak - terror." It is particularly disingenuous for an historian to claim Hamas only "resorted" to terror due to the evil Israelis - as if Hamas had not first used such "weapons of the weak" back in the early 1990s, to sabotage the Oslo peace process. Despicably, others used Holocaust shorthand to berate Israel. Calling Gaza a "big concentration camp," as Cardinal Renato Martino, the Vatican's justice and peace minister, did, or writing in on-line in Spain that "the Machiavellian brain of this entire extermination operation is no different from that which designed Nazi Germany," crossed the line. For starters, the Holocaust - and other genocides - killed thousands, tens of thousands, millions - dwarfing the Palestinian civilian casualties in the hundreds despite three weeks of war. Moreover, there is something particularly dastardly about preying on an ethnic group's historic sensitivities. President Barack Obama will endure much criticism, but if critics make slavery analogies or refer to minstrel shows, their condemnation will be racist. During her campaign, Hillary Clinton and her supporters did not deem attacks on her Iraq war stance sexist. They complained about excessive attention to her clothes, speculation about her grit and other comments invoking stereotypes which historically demeaned women. MANY OF these anti-Zionist attacks resurrected the historic ghost of anti-Semitic essentialism. When asked about his fellow protester in Florida who shouted at Jews, "You need a big oven, that's what you need," one rally organizer initially seemed to disavow the remarks. "She does not represent the opinions of the vast majority of people who were there," Emmanuel Lopez told Fox News. But Lopez quickly added that "Zionism in general is a barbaric, racist movement that really is the cause of the situation in the entire Middle East." Lopez, a state coordinator for ANSWER (Act Now to Stop War and End Racism) engaged in classic racist essentialism. For centuries, critics of Jews have degenerated from criticizing specific Jews' individual actions to generalizing about Jews and Judaism. Generalizing about Zionism's essence condemns Jewish nationalism with this age-old anti-Semitic tactic. A sign at a Melbourne rally took this rhetoric further, crying: "Clean the Earth from Dirty Zionists." You do not need a PhD in Jewish history - or in genocide studies - to see the Hitlerian overtones. Many victims of racism - and most especially the Jews in the Holocaust - were tagged as unclean, thus deserving of extermination, lest the general population be infected. The ugly inverted rhetoric follows its inexorable logic: accusing the victims of the 20th-century's most horrific genocide of committing genocide, then essentializing and demonizing their movement for collective national fulfillment, leads to calls for eradication. (It also excuses Iranian calls for Israel's genocide). Jews have seen this happen too often to be blasÃ© about it, whether the speaker is a Vatican official or a street punk. Essentialism poisons the environment and corrupts other arenas. In the past 40 years, no Western power has engaged in any major military action that did not trigger massive criticism. However, the broad lynch-mob atmosphere against Israel singularly questions its existence, not just the proportionality of its actions. More than 60 years after the country's founding, the world still has the Jewish state on probation, seemingly only accepted when it behaves well. Rogue states like Pakistan - an artificial creation carved out of a crumbling British Raj - do not have their existence questioned, while Israel constantly has to justify itself. It is depressing in the 21st century to see such anti-Semitism, especially among those who designate themselves knights in the fight against racism. But the disproportionate demonization, the idealization of Hamas, the essentialism, the animosity coursing through so much criticism of Israeli actions suggests that the world has yet to heal from one of its most persistent afflictions. The writer is professor of history at McGill University in Montreal. The author of Why I Am a Zionist: Israel, Jewish Identity and the Challenges of Today and Leading from the Center: Why Moderates Make the Best Presidents.