Of all the serious accusations that can be made, calling someone an anti-Semite is among the most serious.

What is it? The United States Holocaust Memorial Museum in Washington — where I have taken ashen-faced school kids on tours, to see the horror that real anti-Semitism causes — is a good place to seek a definition.

The museum simply defines anti-Semitism as “prejudice against or hatred of Jews.”

Hatred of Jews, the museum notes, preceded the coining of the term anti-Semitism in the modern era. Jews had of course been the target of pogroms, violence and discrimination long before anyone came up with a name for it.

Generally, however, “anti-Semitism” is defined as hatred of Jews — Merriam-Webster, Oxford and Britannica all say so.

Calling someone an anti-Semite, without justification, is defamatory — and it could get you hauled into court. In 2008, a former federal Liberal candidate, Lesley Hughes, sued Conservative cabinet minister Peter Kent, B’nai Brith and the Canadian Jewish Congress for suggesting that she had published anti-Semitic articles.

Four years later, the case settled, and the defendants issued a statement that “accepted and affirmed that Hughes is not an anti-Semite.”

An earlier 2001 New Brunswick Court of Appeal case found similarly: Calling someone an anti-Semite is defamatory “on the face of it.”

Brian Shiller is a Toronto lawyer currently litigating a case in which the labelling of someone as an “anti-Semite” is at issue.

“Calling someone anti-Semitic is defamatory,” says Shiller (who, full disclosure, has also been my lawyer in libel cases). “It’s very serious.”

No less than Nobel laureate, and one of the greatest men of our time, Elie Wiesel, agrees: “We must be very careful because to level an accusation of anti-Semitism is the most serious accusation.”

Which leads us to the simply extraordinary speech Prime Minister Stephen Harper made in Jerusalem last week. The speech was extraordinary because Harper, a Gentile, literally took it upon himself to redefine anti-Semitism.

We can speculate as to why he did so. Harper was hoping to curry favour with his Likud Party host, Israeli Prime Minister Benjamin Netanyahu. Or, he was seeking to broaden the political support he enjoys in the Jewish community back home. Or, he honestly believes that any criticism of Israel at all — any — is anti-Semitic. Is it?

Sun Media’s David Akin, and others, certainly interpreted Harper’s speech to the Israeli Knesset as I do. Akin’s story was headlined: “The Harper doctrine: You’re all anti-Semites.”

Reading the speech, the headline is fair. Said Harper: “Intellectualized arguments against Israeli policies” are the “new anti-Semitism.”

That definition goes much, much further than the Holocaust Memorial Museum, dictionaries, and even Elie Wiesel himself. “I could not apply this terrible word to everyone” who periodically criticizes policies of the Israeli government, Wiesel warns.

Indeed it is. The question Harper must now ask himself, then, is whether Nelson Mandela was an anti-Semite — he not-infrequently criticized Israeli government policy as it relates to Palestine.

What of successive popes? The Vatican has held the longstanding view that the Israeli government’s policies with respect to Jerusalem and the territories are wrong-headed.

How about American Jews? A recent Pew survey found that 48% of them were critical, or highly critical, of Israeli government peace policies. Does Harper regard half of America’s seven million Jews as anti-Semitic, too?

And so on, and so on. You can see where this is going. Extending the definition of anti-Semitism might assist Stephen Harper politically, but it doesn’t really help those who are the actual targets of anti-Semitism. In a democracy — and Israel is one — occasional fair-minded criticism goes with the territory. It is the territory, in fact.

“An anti-Semite used to be a person who disliked Jews,” Auschwitz survivor

Dr. Hajo Meyer has said. “Now it is a person who Jews dislike.”

Words worth pondering, prime minister, as you return to Canada today.