The leftist smears against Democratic Senator Charles Schumer for daring to oppose the Iran deal, calling him disloyal, warmongering and seduced by Jewish money, should inspire a new verb. Let’s call being “Schumered” – being branded a traitor for deviating from the party line once, despite a lifetime of party loyalty. The far-right attacks on America’s ambassador to Israel, Dan Shapiro, as a “kapo” for daring to support the Iran deal are more sickening. Shapiro’s smearing is a libelous Schumering of an excellent ambassador and a warm friend of Israel, adeptly navigating the US-Israel relationship during this tense time.The Iran deal demands passionate debate, but this is ridiculous. Dissenting Democrats opposing the Iran agreement are not advocating war; not seduced by the mysterious “lobbyists” President Barack Obama targeted; not “making a common cause” with the Iranian hardliners, as Obama, I mean “Israel’s Best Friend Ever,” appallingly charged; not following the money; not serving Israel; not embracing Republican foreign policy. Nevertheless, CNN’s Fareed Zakaria suggested that Schumer feared that by supporting the deal, “he wouldn’t be able to raise as much money...among, perhaps, you know, wealthy supporters.”Yes, we know exactly what Zakaria and Obama mean. Less subtly, a Daily Kos cartoon mocked Senator “Woodchuck” Schumer – flanked by an Israeli flag.The vicious partisanship that started during Bill Clinton’s 1990s continues. Many ignore former New York City mayor Ed Koch’s advice: “If you agree with me on nine of 12 issues, vote for me; if you agree with me on 12 of 12 issues, see a psychiatrist.” Schumer’s Schumering reflects Democrats’ Obama Omerta: squelching critics and demonizing them as evil, even racist. John Kerry’s hysteria reinforces this code of silence, as America’s secretary of state predicts lost American credibility, war, even the dollar’s fall if his precious deal fails. Bizarrely, many deal supporters – including Obama – seem much more offended by Israel’s opposition than by Iran’s threats to destroy America.Regrettably, there is a whiff of anti-Semitism in some attacks against the deal’s attackers, recycling canards about Jewish money, dual loyalty, and power, as Israel is targeted as the deal’s only foreign opponent, despite Saudi and Egyptian opposition too.As an opponent of the deal, I wish my allies shamed the other side by making their points civilly, attacking the deal and the ayatollahs who will benefit without maligning the deal’s supporters. Alas, the partisan attacks against Obama have been equally unhinged.It’s ridiculous to call Obama and all of the deal’s supporters “anti-Israel”; they are just wrong. We need new labels beyond “anti-Israel” to acknowledge legitimate criticism from supporters of the Jewish state who dislike its current government and trajectory. The all-ornothing rhetoric foolishly risks turning mild skeptics into anti-Israel zealots.I understand opponents’ fears of a nuclear- empowered Iran, and especially Jewish fears. Jews take threats to hurt us seriously because we have been seriously hurt following such threats. Still, we cannot combat sloppy Holocaust comparisons, then make them ourselves.It is particularly infuriating to hear that some far-right Israelis called an honest and good person like Dan Shapiro a “kapo.” No self-respecting Zionist would use that analogy, nor would any thinking person. The hooligans who used that word against this honorable man have separated themselves from the Israeli and Jewish consensus. They should be shunned – except these sniveling cowards made their threats anonymously.I invite all civilized members of the pro-Israel community to defend Ambassador Shapiro, saying “you slur him, you slur me.” We both support America and Israel, even if we disagree occasionally – with each other, or with others about how best to keep both countries safe in a dangerous world.In this world of Islamic State and Iran, of terrorist-enabling, boycotting-pushing, Boycott, Divestment and Sanctions (BDS) far-leftists and of bigoted, sometimes murderous, far-rightists, we must do a better job of distinguishing good guys from bad guys. Most Iran-deal opponents and Iran-deal supporters are well within America’s liberal democratic and pro-Israel consensus. We need a broad pro-Israel tent of tolerance making shrewd, effective coalitions, supporting Israel’s right to exist even while arguing about certain policies.I applaud Hillel president Eric Fingerhut’s recent meeting with J Street students to discuss joint strategies for combating BDS because we need a Left-Right coalition to fight the boycott, led by progressive students who criticize Israel’s occupation but, unlike BDSers, support Israel’s existence. And I salute Senator Schumer and other Democrats for following their consciences and not their party to fight the Iran deal.Ultimately, the whole Iran debate has been distorted. Prime Minister Benjamin Netanyahu has foolishly made this American problem seem like a provincial Israeli worry. American Jews are mimicking Netanyahu’s error by fighting the deal – or supporting it – as Jews and through Jewish organizations rather than as Americans through non-denominational parties. I don’t care that the Chicago Jewish Federation opposes the deal. And the 340 rabbis urging Congress to embrace this deal should devote their energies to building Jewish life more than playing politics, to urging congregants to embrace Shabbat or Jewish values rather than lobbying legislators in their rabbinic robes.While American and Israeli Jews should debate freely, passionately, the Iran nuclear deal is ultimately a world issue, a Western issue, not “just” a Jewish issue or Israeli issue.As an American, I feel threatened when Iran’s dictators orchestrate demonstrations shouting “Death to America.” Didn’t we learn on September 11, 2001, to take Islamist threats seriously? Didn’t we learn that Islamism and terrorism are not “just” Israel’s problems but America’s problems too? Democrats and Republicans must remember: the true enemy is Iran not the other party.Let’s have a passionate, civil, thought-provoking debate. Let’s focus on what’s best for America – which will be best for the world.And let’s stop Schumering and demonizing, Left and Right.The writer is the author of The Age of Clinton: America in the 1990s which will be published this October by Thomas Dunne Books of St. Martin’s Press. A professor of history at McGill University who will be a Visiting Scholar at the Brookings Institution this fall, this will be his eleventh book.Follow on Twitter @GilTroy.