As an organization committed first to combat anti-Semitism but also to work against all forms of prejudice, the Anti-Defamation League often talks against a “hierarchy of hate,” a competition for victimhood among minorities. Our philosophy is that the emphasis should fall on the commonalities of those who are targeted for hate as the best way to form strong coalitions.

Every once in a while an event takes place, however, that jars us out of that kind of approach. The speech by President Ahmadinejad of Iran before the United Nations General Assembly on September 23 is one such event.

It is not that anything that comes from the mouth of Mr. Ahmadinejad shocks. After all, he has denied the Holocaust.

It is, rather, the realization that the most lethal form of hatred that could be directed against the Jewish people was delivered from the platform of the United Nations and that no other such diatribe against any other religious or ethnic group could possibly flow from that august site.

With all the discussion that has surfaced in recent years as to when anti-Zionism becomes anti-Semitism, Mr. Ahmadinejad’s tirade had little to do with that. Instead, he returned to the language that appeared in the infamous forgery, the “Protocols of the Learned Elders of Zion,” that was used by Adolf Hitler to persecute and eventually murder millions of Jews. It is the notion that the Jews, though small in number, control all the sources of power and influence in the world in order to further their own interests at the expense of everyone else. And, when problems emerge, of course, it is the Jews’ fault.

Listen to Mr. Ahmadinejad: “Although they [Zionist Jews] are a minuscule minority, they have been dominating an important portion of the financial and monetary centers as well as the political decision making centers of some European countries and the U.S. in a deceitful, complex, and furtive manner.”

This is the classic charge against the Jewish people that is at the root of why anti-Semitism has been so enduring and so lethal. The “secret, evil power” of the Jews can be conjured up any time there is a crisis. And so we’ve seen it in our time, first with the terrorism of September 11, 2001, when Jews were accused of committing that dastardly act, then with the war in Iraq, and now with the financial meltdown on Wall Street.

And it is such a lethal form of hatred because it does not merely suggest that one should dislike Jews, but rather that one needs to defend oneself against the “all-powerful, poisonous Jew.” Once one accepts the assumptions of the “Protocols” or of Mr. Ahmadinejad, then anything goes. Even the destruction of the Jewish people, as took place under Hitler, or the use of a nuclear weapon against the Jewish homeland, as is threatened by Iran. Mr. Ahmadinejad’s focus on the Jews as the source of evil in the world sets the stage for the justification of what’s to come. That’s why his speech was not just one more diatribe from a “crazy” leader.

There is no more dangerous brew of ingredients in the world than this. And yet, Mr. Ahmadinejad was able to deliver these words at the General Assembly, at the very place that was created in response to the end-product of this kind of lethal hatred, the Holocaust.

And the representatives of the nations did not walk out in protest: many even applauded him at the conclusion of his address.

It makes one wonder. Have all the Holocaust memorials, commemorations, books, and films really sunk in? What does “Never Again” mean when the United Nations is used to reiterate the very themes that were the basis for what happened in the 1930s and 1940s? And all this while Iran is getting closer to achieving a capacity to produce enriched uranium and build nuclear warheads.

It is said again and again that Iran is not a Jewish issue but one for the world’s safety and security. And it is. But as we watched the spectacle at the United Nations, it’s hard to avoid the conclusion that the Jews are being left out there once again.

Mr. Foxman is National Director of the Anti-Defamation League and author of “The Deadliest Lies: The Israel Lobby and the Myth of Jewish Control.