The worldwide Jewish community can be thin skinned about criticism of the policies of the state of Israel, but the vitriol reached a new low last week. After members of the South African Jewish community threatened to disrupt the ceremony if he attended, Justice Richard Goldstone, author of a controversial United Nations report on the conflict in Gaza, canceled plans to attend his grandson's upcoming bar mitzvah ceremony in Johannesburg.

The Goldstone report, released in September, concluded that both Israel and Hamas committed war crimes during the conflict in Gaza in late 2008 and early 2009, and that both had deliberately targeted the other side's civilian population in attempts to achieve their goals. It recommended criminal investigation and possible prosecution of those found responsible.

It is completely appropriate for critics to scrutinize, question and discuss the facts and conclusions of the Goldstone report. Intellectual and political dispute is deeply woven into Jewish learning, tradition and communal life, and the welfare of the state of Israel rightly engages the deepest passions of the Jewish people.

But prominent critics of the report quickly made the leap from debate to invective. Israeli President Shimon Peres called Goldstone "a small man, devoid of any sense of justice." Alan Dershowitz of Harvard Law School called him "a traitor to the Jewish people." An Israeli minister and numerous blog posts have labeled him an anti-Semite.

And now this. Threats that his grandson's bar mitzvah would be disrupted if he attended have forced Goldstone to make the agonizing decision to stay away from one of the sacred milestones of his grandson's life.

One leading rabbi explained the feelings of members of the South African Jewish community to the Center for Law and Justice: "[T]hey believe he put Israel in danger, and they wouldn't like him to be getting honor" by being called to the altar as part of the bar mitzvah ceremony. Goldstone clearly felt that after seven months of personal attacks, he could not put his family through yet another ordeal.

This is a man who courageously challenged apartheid in his native country two decades ago; who helped build the first international war crimes courts since Nuremburg; who last year won the MacArthur Foundation Award for International Justice; and who has served on the board of governors of Hebrew University. Goldstone currently chairs the advisory board of the International Center for Ethics, Justice and Public Life at Brandeis University, which I direct.

This incident did not come out of the blue. And it is not just about one man's family occasion or about the content of one United Nations report. It grows out of a climate in which defenders of Israeli government policy have increasingly resorted to personal attacks on the government's critics. Jewish leaders around the world should decry the kind of personal attacks Goldstone has endured and speak out more forcefully against those who resort to personal attacks in an attempt to delegitimize Israel's critics.

It is especially important that those who disagree with the Goldstone report make clear their opposition to such personal attacks. Rep. Gary Ackerman of New York, who has led the opposition to the Goldstone report in the U.S. Congress, should be commended for his letter of outrage to the South African Zionist Federation. Others should follow suit.

Preventing Goldstone from attending his grandson's bar mitzvah isn't standing up for Israel. Labeling Jewish critics of Israel as traitors or anti-Semites isn't standing up for the Jewish people. Such steps are instead a brand of hatred that represents a direct assault on Jewish values of tradition and justice and conscience.