See the latest opinion pieces on our pageHe would have been furious with President Barack Obama’s negotiating approach, seeming more anxious for an agreement than Tehran was, and more concerned with reassuring Iran than defending American dignity when attacked.Moynihan warned that words matter. He refused to ignore verbal threats against America or its allies.Moynihan proved that sometimes taking offense is the best defense. Imagine how much Obama would have accomplished diplomatically and politically if he had walked away from the table when Iran’s mullahocracy called for America’s destruction. Such boldness would have improved the deal and so boosted Obama’s popularity he could have sold even a weaker agreement. The campaign against this agreement should bombard American airwaves with footage of Iranians threatening America – reminding Americans what this regime thinks of us.A scrappy New Yorker, a World War II veteran and an eloquent Cold Warrior, Moynihan realized that oppressive, aggressive totalitarians threatened the world’s freedom- loving, peace-seeking democracies. Democracies weren’t perfect – but find their equals, he said. Democracies had to look out for one another. He understood that hatred of Israel usually reflected hatred of America and of core democratic values. In defending Israel and America, he and his allies were defending universal human rights. His opposition to the UN’s Zionism-is-racism resolution, the anti-Zionist movement’s Rosetta Stone – calling it anti-Semitism, invoking human rights to defend Israel’s right to exist – shows how to combat the modern Boycott, Divestment, Sanctions (BDS) movement, which supports those who still wish to deprive the Jewish people of their ancestral homeland.Moynihan’s principled, proud diplomacy clashed with the US State Department’s conciliatory approach.As such, ambassador Moynihan remained ambassador only eight months. But his ardent defense of America made him a pop star, and a popular four-term senator from New York.Continuing to defend America as a senator, Moynihan emphasized something else Obama apparently forgot: Congress counts too; the Constitution does not make the president a foreign policy soloist. As Obama rushes his agreement to the UN Security Council while resisting Congress’s constitutionally sanctioned input, Democrats should remember that the Iran-Contra scandal (which began with Republicans’ deluded outreach to Iranian “moderates”) stemmed from Congress asserting its power to handcuff the president occasionally (in that case regarding funding the Nicaraguan contras). Democrats and Republicans should both be more consistent in respecting the constitutional checks and balances, even if it impinges on their prerogatives when dominant.While teaching that diplomacy can be muscular not just wimpy, that words matter, that totalitarian threats must be faced, that democracies should unite, and that Congress counts, Moynihan taught that history is malleable.He believed that individuals, organizations and movements can make history. In 1975, he and his Israeli UN colleague Chaim Herzog mobilized the democratic world against the UN’s Zionism-is-racism resolution.Sixteen years later, he and Herzog helped make the impossible possible: thanks to pro-Israel, anti-totalitarian, bipartisan cooperation with heaps of what the American Jewish Committee’s David Harris calls “nudnik diplomacy” – from the grassroots too – the UN General Assembly, while still hostile to Israel, repealed the 1975 Zionism-is-racism resolution. Jewish organizations – and all pro-American organizations, including both major political parties – should learn from Moynihan that supporting Israel, containing Iran, defeating this boycott movement – are all-American issues, not simply Jewish issues. That the Iran deal is viewed as an Israel issue is absurd; the mullahs threaten America directly. Note that taking on seemingly quixotic causes like fighting the Zionism-is-racism resolution in 1975 or 1991, like opposing this year’s Iranian nuclear sellout, like defending Israel and Zionism on campus, can also succeed, while doing right offers its own reward.This important 40th anniversary year, let’s teach Moynihan’s words – and those of his colleague Chaim Herzog – in their eloquent twin defenses of Zionism.Let’s mimic his tactics, deploying a range of diplomatic weapons to preserve democracy vigorously, effectively.And, in Israel, it’s time to honor this great anti-totalitarian, pro-freedom friend of Israel, the Jewish people, and democracies worldwide by finally, belatedly, naming a street in Jerusalem, the Jewish people’s capital, after our friend, role model and champion, Daniel Patrick Moynihan.The writer is the author of The Age of Clinton: America in the 1990s, to be published by Thomas Dunne Books/ St. Martin’s Press in October 2015. A professor of history at McGill University, he will be a Visiting Scholar at the Brookings Institution in the fall. His previous book was the award-winning Moynihan’s Moment: America’s Fight Against Zionism as Racism. Follow on Twitter @GilTroy and www.ageofclinton.com.