WASHINGTON—The link between hatred of Jews and of the only Jewish state often requires little conjecture. This is particularly so in the Arab world, where cultivated popular anti-Semitism has been ignored abroad as an impetus of regional conflict.

For evidence that anti-Israel sentiment in the Middle East is not merely characterized by sharp political differences, but instead mimics and is fueled by the most defamatory and dangerous of historical anti-Jewish themes, we need look no further than a widely published political cartoonist, a Jordan-based Palestinian named Emad Hajjaj. His cartoons regularly feature blatant incitement, equating Israel with the Third Reich, crudely caricaturing Jews (distinguished by religious garb and symbols) as bloodthirsty monsters, portraying menorahs as weapons and showing the “crucifixion” of Palestinians on a cross marked by a Star of David.

None of this is exceptional. What is surprising, or should be, is the international indifference to—indeed, complicity in—vile and incendiary Arab anti-Semitism without parallel, quantitatively or qualitatively, on the Israeli side of the regional divide. Yet B’nai B’rith has found that among those claimed as clients by Hajjaj’s public relations firm Abu Mahjoob Creative Productions Company are not only several local government bodies but also foreign organizations such as the British Council and the major corporations Visa, Orange, Ferring Pharmaceuticals and the German industrial giant Siemens. If this were not bad enough, the firm’s client list features multiple agencies of the Quartet-member United Nations—including the United Nations Development Fund for Women (now merged into U.N. Women), the United Nations Development Programme and the United Nations Children’s Fund, or UNICEF.

Hajjaj’s open record of abundant anti-Semitic output makes it unlikely that prominent clients have been unaware of patronizing a hatemonger. His cartoons have been included in U.S. State Department reporting on anti-Semitism, and the U.N. Human Rights Council’s notorious special rapporteur on the Palestinians, Richard Falk, recently posted an anti-Semitic, anti-American Hajjaj cartoon on his blog. Falk, in a new post, has again celebrated the abandonment of diplomacy in favor of anti-Israel boycotts, divestment and sanctions. This “authoritative” U.N. figure’s agitation is especially unhelpful when even some American civil society groups, such as elements of the Presbyterian Church (USA) and the United Methodist Church in the run-up to their national conventions this year, urge economic leverage as a means to single out Israel for pressure and isolation.

Sadly, there can be little dispute of the ubiquity and intensity of anti-Semitism in Arab and other Muslim-majority lands. After all, these are the societies where remarkably many folks continue to believe that 9/11 was a Zionist plot, that the Holocaust is a fabrication, that a now-despised native son such as Muammar Gadhafi was Jewish and that Jews are fated to violent subjugation as the “sons of apes and pigs.” It then becomes a bit more understandable, if no less frightening, that two random Israeli boys, happened upon by random Palestinians, could be stoned to death in 2001.

The relative paucity of Jews has also not disincentivized terrorist attacks over recent years at synagogues and other Jewish sites in Istanbul, Turkey; Casablanca, Morocco; Khashef, Yemen; and Djerba, Tunisia, let alone Hezbollah’s atrocities as far away as Argentina.

People expressing reasonable, measured criticism of Israel cannot, of course, be considered anti-Israel or anti-Semitic. However, animus to Zionism itself—simply the existence of the democratic Jewish state—frequently betrays denial of Jews’ basic rights and history.

Natan Sharansky has identified three elements that signal where criticism of Israel crosses over into bigotry: delegitimization, double standards and demonization. In 2005, the European Monitoring Centre on Racism and Xenophobia (now known as the European Union Agency for Fundamental Rights) essentially echoed these terms. The Vatican, too—in its official dialogue with Jews in 2004 and, more subtly, in the document “The Church and Racism,” distributed at the United Nations’ now-infamous 2001 Durban conference on racism—has recognized the clear correlation between anti-Zionism and anti-Semitism.

While anti-Semitism has existed in many regions, the modern Arab world stands out with the dramatic flight of its Jews. The Jewish population in Arab countries has dropped from some 800,000 six decades ago to perhaps 6,000 today, not to speak of the exodus from neighboring non-Arab Muslim countries. These numbers don’t lie. The Pew Global Attitudes Project has confirmed unfathomable antipathy toward not merely Israel but “Jews” both in Arab states and non-Arab Muslim states far removed from any territorial dispute with Israel. In all but one of the seven nations surveyed, 96 to 98 percent of respondents had negative views of Jews; in Indonesia, a slightly less commanding 91 percent shared this outlook.

Needless to say, the kind of dehumanization to which so many mainstream Arab opinion-shapers subject Israelis and Jews would not be tolerated against other groups.

In the pursuit of justice and coexistence, non-selectivity in tackling prejudice is vital. The Jewish community has often been at the forefront of challenging mistreatment of Christians, Muslims and those of other faiths. While much of the world is willing to turn a blind eye to key barriers to reconciliation in the Middle East, let us ensure that no institution is unaccountable for complicity in these foremost impediments to peace.