Ira Stup was raised in Philadelphia attending Jewish day school and camps. He found his home in the Jewish community and was “intoxicated with Jewish democracy” as framed in the ideals of Israel’s foundation. Now he has returned deeply troubled from a one-year fellowship based in Tel Aviv.

The worst single incident occurred on Ben Yehuda Street in central Jerusalem. Stup, 24, a Columbia graduate, was returning from a rally with a couple of friends carrying a banner that said, “Zionists are not settlers.” A group of religious Jews wearing yarmulkes approached, spat on them and started punching.

“About 20 people saw the whole thing and just watched. They were screaming, ‘You are not real Jews.’ Most of them were American. It was one of the most disappointing moments of my life — you can disagree as much as you want with a banner but to allow violence and not react is outrageous. For me it was a turning point. Nobody previously had said I was not a real Jew.”

The view that American Jews supportive of Israel but critical of its policies are not “real Jews” is, however, widespread. Israel-right-or-wrong continues to be the core approach of major U.S. Jewish organizations, from the American Israel Public Affairs Committee (Aipac) to the Conference of Presidents of Major American Jewish Organizations.

To oppose the continued expansion of settlements in the West Bank (“Zionists are not settlers”), or question growing anti-Arab bigotry as personified by Israel’s rightist foreign minister and illustrated by the “loyalty oath” debate, or ask whether the “de-legitimization” of Israel might not have something to do with its own actions is to incur these organizations’ steady ire.

Debate remains stifled, despite Peter Beinart’s important piece this year in the New York Review of Books describing growing alienation among young American Jews asked to “check their liberalism at Zionism’s door.” Oh, sure, you can find all sorts of opinions about Israel all over the place; America remains an open society. But Aipac has systematically shunned a debate with J Street, the upstart Jewish organization that supports Israel, opposes the settlements and attempts to reclaim the progressive ideals of Zionism by saying that the systematic oppression of the Palestinians undermines Israel.

“These organizations’ view remains essentially that any time you engage in an activity critical of Israel you are trying to destroy the state of Israel,” Jeremy Ben-Ami, the president of J Street, told me. “Here are all these Jewish kids being raised on great liberal values at Hebrew schools — walks for the homeless, Darfur, AIDS — but God forbid we talk about what’s happening in Israel! It’s a dynamic that cuts off discourse.”

The issues are worth debating at the highest level. Middle East talks have just broken down again, precisely over settlements. President Barack Obama had virtually no domestic constituency for his attempt to denounce the continued growth of settlements as unacceptable and as undermining a two-state peace at its core: land.

Obama was left dangling, more so after the midterms, and had to retreat. This is not merely a failure of the parties. It is a failure of U.S. politics and the way those politics are straitjacketed by an Israel-right-or-wrong mantra that leads inexorably, over time, to one state with more Arabs in it than Jews. What then will remain of the Zionist dream?

Stup’s research took him often to the West Bank. He would come back to Tel Aviv and talk about Palestinian humiliation he’d seen and found that Israelis seemed unaware or unconcerned. He read in one newspaper that 53 percent of Israeli Jews would encourage Israeli Arabs to leave — “and I saw and felt that anecdotally.”

A painful question hardened: “Seeing what the occupation looked like, and given the ideals of Jewish democracy I was raised on, I wondered: Could Israel be failing and could we American Jews be defending that failure?”

It’s time to think again and, above all, think openly. Last month, Ben-Ami was scheduled to speak at a Reform Jewish synagogue, Temple Beth Avodah, in Newton, near Boston. At the last minute the event got canceled because of what the rabbi described as strong opposition from a “small, influential group” within the congregation.

Jewish groups, or Hillel societies, on U.S. campuses sometimes discover they will lose their biggest donors if they allow a J Street youth group to form within them.

Last month, Prime Minister Benjamin Netanyahu, speaking to the Jewish Federations of North America in New Orleans, was heckled by protesters holding banners suggesting the occupation and loyalty oaths de-legitimize Israel. Their banners were ripped (with teeth) and the young Jews dragged out. Where an important conversation could be held, confrontation prevails.

Stup, moved to act, has joined J Street. This decision caused tremendous pressure on his family back in Philadelphia. One very close family friend came over to his mother’s house recently and accused him of “poisoning the minds of young Jews.” The friendship has been strained to breaking point.

“Why,” Stup asked me, “is it poisoning minds to encourage them to think critically about the actions of the Israeli government?”