Never has it been more difficult for Prime Minister Benjamin Netanyahu of Israel to convince the world that, as he put it in 2006: “It’s 1938. Iran is Germany.” He tried again at the United Nations this week. In a speech that strained for effect, he likened Iran to a 20th-century “radical regime” of “awesome power.” That would be the Third Reich.

Among those who question this approach is David Harris, the executive director of the American Jewish Committee. Referring to the new Iranian president, Hassan Rouhani, he wrote in the Israeli daily Haaretz that, “Simply implying, for instance, that anyone who sits down with Rouhani is a modern-day Neville Chamberlain or Édouard Daladier won’t do the trick. To the contrary, it will only give offense and alienate.”

When Netanyahu’s staunchest supporters — the leaders of the American Jewish community — question his approach to Iran, the Israeli prime minister needs to stop calling Rouhani “a wolf in sheep’s clothing,” his favored epithet, and start worrying about crying wolf.

It is not just that the world has now heard from Netanyahu of the imminent danger of a nuclear-armed Iran for a very long time. It is not just that Israel has set countless “red lines” that proved permeable. It is not just that the Islamic Republic has been an island of stability compared to its neighbors Syria, Iraq and Afghanistan. It is not just that, as Rouhani’s election shows, Iran is no Nazi-like totalitarian state with a single authority but an authoritarian regime subject to liberalizing and repressive waves.