Anne Bayefsky records the stance of Human Rights Watch at the 2001 UN Durban conference:

As we arrived at our meeting the chief Durban representative of Human Rights Watch, advocacy director Reed Brody, publicly announced that as a representative of a Jewish group I was unwelcome and could not attend. The views of a Jewish organization, he explained, would not be objective and the decision on how to vote had to be taken in our absence. Not a single one of the other international NGOs objected.

Update: Reed Brody responds here, but doeson't contradict Bayefsky's basic points:

....In Durban, and its year-long run-up, we campaigned to ensure that the WCAR would be about more than the Middle East. ..... A great achievement of the WCAR process was the unprecedented mobilization of victims of racism from communities around the world, such as the so-called untouchables of South Asia, the Roma of Europe, and blacks in Latin America.

With over 3,000 victims groups present in the pre-WCAR forum of nongovernmental organizations (NGOs), organizations like Human Rights Watch and Amnesty International had limited ability to moderate the language of chapters for the NGO declaration. Each chapter was drafted by the affected community, including not only Palestinians but also such groups as Tibetans, Kurds, and Dalits. Many of these chapters were factually supported, powerful documents, but others were not. Our refusal to participate in the voting on the statement and its chapters, and our failed attempt to cast the document as a collection of the "voices of the victims" rather than as a text endorsed by all, was intended precisely to avoid giving a stamp of approval to all parts of the document.

Bayefsky, however, claims that we "said nothing" as the final NGO statement was put together on September 2, 2001, and lent legitimacy to its inflammatory statements about Israel. In fact, as the Post (and virtually every other newspaper in the world) reported on September 3, "The New York-based Human Rights Watch condemned the resolution." The Post quoted me as saying, "Israel has committed serious crimes against the Palestinian people, but it is simply not accurate to use the word genocide and wrong to equate Zionism with racism."

Prior to the declaration's adoption I personally spent hours trying to persuade Arab and Palestinian colleagues to amend this and other language. ....

Brody doesn't address Bayefsky's claim that he announced that her Jewish group was "not objective" and could not participate in the NGO meeting. So we can regard the account as confirmed. And Brody's condemnation of the resolution was made afterwards and not during the proceedings as Brody tries to suggest:

The declaration, adopted by a majority of the 3,000 delegates from 44 regions to the World Conference's Non-Governmental Organization (NGO) forum -- a broad-based summit of groups from around the world involved in human rights issues -- shocked Jewish participants, and many walked out of the meeting.
Some other international human rights groups who were part of the NGO forum, including Amnesty International and Human Rights Watch, moved to distance themselves from the declaration.
...
Reed Brody, executive director of the New York-based Human Rights Watch, said: "Israel has committed serious crimes against Palestinian people but it is simply not accurate to use the word genocide and to equate Zionism with racism ... it is now a matter of damage control."