We recently commemorated the 65th anniversary of the liberation of Auschwitz. The somber anniversary was marked by customary calls to combat anti-Semitism worldwide. Yet resisting bigotry is not as clear-cut as it might seem, at a time when the very definition of anti-Semitism is shifting and constantly questioned. Where some see the cancer of Jew-hatred, others see the charge of anti-Semitism to stifle discussion of issues, particularly in relation to Israel and the Middle East.

Anti-Semitism is probably the world’s oldest still-extant form of group hate. But where does legitimate opinion end and bigotry begin? Israeli Information Minister Yuli Edelstein told the media that the recent United Nations report harshly critical of Israel’s military operations in Gaza in December 2008-January 2009 was a type of anti-Semitism, although its author, South African judge Richard Goldstone, is Jewish. Commentators have criticized the Goldstone report as tendentious, particularly in downplaying Hamas’ fighters practice of hiding among civilians. But if the anti-Israel bias is real, is it based on anti-Semitism or on a left-leaning prejudice that favors Third World people over Western democracies and their allies? The latter seems more likely.

Yet, if it’s too simplistic and unfair automatically to equate critiques of Israeli policies with anti-Jewish prejudice, critiques of Israel often serve as a convenient smokescreen for genuine bigotry. Attacks on the Israel Lobby have a tendency to descend into nasty insinuations about Jewish control of major American institutions and American Jews as disloyal.

Michael Scheuer, former head of the CIA’s Bin Laden unit, has portrayed himself as a victim of the Israel Lobby, charging that he was fired by the Jamestown Foundation, a Washington, D.C. think tank, over a caustic remark about Barack Obama pandering to Israel backers during the 2008 campaign.

On Jan. 4, Scheuer appeared on a C-SPAN program where a caller declared that he was sick and tired of all these Jews pushing us to go to war against our Muslim friends and went on to say, “They have way too much power in this country. People like [Paul] Wolfowitz and [Doug] Feith and the other neo-cons they jewed us into Iraq.” Scheuer not only failed to condemn this bigotry but seemed to agree.

FEAR OF BEING LABELED ANTI-SEMITIC SHOULD NOT STIFLE DEBATE ABOUT ISRAELI POLICIES.

Hostility to Israel in the Arab and Muslim world often manifests itself in updated versions of ancient, vicious libels against Jews. Thus, the medieval blood libel claiming that Jews kill Christian children to use their blood for ritual purposes finds new life in a story peddled by government-run Iranian television station charging that Israeli doctors helping earthquake survivors in Haiti are really there to harvest human organs.

Real anti-Jewish bigotry seems to be on the rise. Traditional right-wing anti-Semitism, based on religious and cultural prejudice and on the perception of Jews as rootless and subversive, often overlaps with a new left-wing anti-Semitism that sees Jews as proxies for Israel, and Israel as a carrier of Western imperialism.

Combating these trends from the bully pulpit is important. Yet President Obama’s recently appointed special envoy and head of the Office to Monitor and Combat Anti-Semitism, Hannah Rosenthal, has reserved her most outspoken criticism so far for Israeli’s United Nations ambassador, Michael Oren, whom she blasted in December 2009 for harsh remarks about pro-peace Jewish groups.

Fear of being labeled anti-Semitic should not stifle debate about Israeli policies or U.S. Mideast policy. But no debate should ever be allowed to become a cover or an excuse for hate and, in this particular debate, there’s plenty of hate to go around.

CATHY YOUNG is a contributing editor at Reason magazine.