Matt Yglesias nails it:
My sense is that what’s really going on here is the same as what’s happening with pro-Israel groups’ years-long campaign against Human Rights Watch. It’s simply not possible to do a credible job of international human rights monitoring without criticizing Israeli behavior now and again. Exercising sovereign authority over the lives of millions of stateless persons is a human rights fiasco waiting to happen. But a lot of Jewish organizations in the United States seem to take the view that because Israel’s human rights record is better than, say, Sudan’s (and it sure is better) that any criticism of Israel amounts to anti-Israel bias.