More than 90 years ago, when Turkey was still part of the Ottoman Empire, Turkish nationalists launched an extermination campaign there that killed 1.5 million Armenians. It was the 20th century’s first genocide. The world noticed, but did nothing, setting an example that surely emboldened such later practitioners as Hitler, the Hutu leaders of Rwanda in 1994 and today’s Sudanese president, Omar Hassan al-Bashir.

Turkey has long tried to deny the Armenian genocide. Even in the modern-day Turkish republic, which was not a party to the killings, using the word genocide in reference to these events is prosecuted as a serious crime. Which makes it all the more disgraceful that United Nations officials are bowing to Turkey’s demands and blocking this week’s scheduled opening of an exhibit at U.N. headquarters commemorating the 13th anniversary of the Rwandan genocide because it mentions the mass murder of the Armenians.

Ankara was offended by a sentence that explained how genocide came to be recognized as a crime under international law: “Following World War I, during which one million Armenians were murdered in Turkey, Polish lawyer Raphael Lemkin urged the League of Nations to recognize crimes of barbarity as international crimes.” The exhibit’s organizer, a British-based antigenocide group, was willing to omit the words “in Turkey.” But that was not enough for the U.N.’s craven new leadership, and the exhibit has been indefinitely postponed.

It’s odd that Turkey’s leaders have not figured out by now that every time they try to censor discussion of the Armenian genocide, they only bring wider attention to the subject and link today’s democratic Turkey with the now distant crime. As for Secretary General Ban Ki-moon and his inexperienced new leadership team, they have once again shown how much they have to learn if they are to honorably and effectively serve the United Nations, which is supposed to be the embodiment of international law and a leading voice against genocide.