But that unspoken rule is now being challenged. As the Middle East boils, Jews critical of Israel's policies in the Palestinian territories are increasingly being heard, and dozens of groups called "Jews for a Just Peace" have sprung up across the country.
This week, a group by that name, formed recently in Durham and Chapel Hill, raised the debate by inviting a lieutenant in Israel's Defense Forces to speak to the Jewish community about his refusal to fight in the occupied territories. Lt. Itai Swirski is one of an estimated 490 Israeli reservists who are spending their obligatory military service in prisons rather than in the West Bank and Gaza Strip. His appearances before Jewish students at Duke and at the University of North Carolina at Chapel Hill drew large crowds, and in a sign of new openness, he has also been invited to speak at three synagogues.
"I think it's good for the community to hear his opinions," said Rabbi John Friedman of Judea Reform Congregation in Durham, where Swirski spoke Friday night. "Those who stay away are making a mistake. Whatever their views, conversation needs to be opened."
Of course, there are many who instinctively recoil at any criticism of Israel. They believe Israel is waging a war of survival and those who resist are violating the law and leaving other Jews at risk.
"I wouldn't even shake hands with a person like that," said Leon Dworksy, a lifelong member of the Durham Jewish community. "In my way of thinking, he's a traitor."
"I've listened to too many people say they didn't think they could be good Jews if they didn't support Israel," said Margaret Lewis of Durham, a member of the Chapel Hill Kehillah, who attended Swirski's talk Thursday.
In his talks, Swirski makes no bones about his love for his country. A 28-year-old labor lawyer, Swirski was born in Israel and served for four years in an an elite paratrooper unit where he was a platoon commander.
Thursday night, Swirski told a rapt audience at the Freeman Center for Jewish Life at Duke University that after several months of reserve duty in the West Bank and Gaza Strip he finally came to the conclusion he could no longer contribute to what he called "the discrimination and humiliation of an entire people." He told agonizing stories of entering Palestinian homes in the middle of the night and yanking family members out of bed, chasing after children who throw stones, and standing guard at home demolitions as children pried toys from the rubble that was their home.
"Serving in the occupied territories, we encourage more hatred," said Swirski. "I saw this hatred in the Palestinian eyes and I didn't want to create more of it."
From a historical perspective, American Jewish criticism of Israel is not new, said Yaacov Ariel, a professor of religion at UNC-CH. Before World War II, it was common for American Jews to question the need for a Jewish state. There was even an organization dedicated to combating the influence of Zionism in American Jewish culture. All that changed as news of the destruction of European Jewry travelled across the ocean.
"With the Holocaust, there was a major change -- a warming of the heart -- toward an independent Jewish commonwealth," said Ariel. The Six-Day War in 1967 galvanized American Jewish opinion in favor of Israel and saw the creation of vigorous lobbying efforts on behalf of whatever positions the Israeli governments embraced.
That consensus began to crack with Israel's invasion of Lebanon in 1982, and it continues today, Ariel said.
But members of Jews for a Just Peace say that although they are opposed to the Israeli government's policies, they are not opposed to the state of Israel.
"We at Jews for a Just Peace North Carolina believe we act in the best interest of Israel if we advocate for a resolution that will bring lasting peace and security," said Tom Stern of Durham, a member of the group. "It's an act of love for the future of Israel."