Prompted by the controversy over Mearsheimer and Atzmon, Bob from Brockley has a good post on anti-Semitism, including this discussion of non-anti-Semitic anti-Zionism, with my added emphases:
Anti-Zionism that also takes a consistent opposition to all nationalisms (including Palestinian nationalism) is not antisemitic; Jewish religious anti-Zionism such as that of the Satmer Hasidim is not antisemitic; Jewish anti-Zionism which rejects the Zionist solution to the questions of Jewish survival and continuity (such as the position of the Jewish Socialist Group or others in the tradition of the Bund, folkism and other diasporist traditions) is not antisemitic [Editor: though one wonders about the relevance of these traditions in 2011, when there is an existing Jewish state with almost eight million citizens]; anti-Zionism from the perspective of Israeli citizens (Jewish or Arab) who want to see Israel as a democratic state for all its citizens (rather than a Jewish state) is not antisemitic; finally anti-Zionism which sees Zionism as a form of imperialism and takes a consistent opposition to all imperialisms without singling out Zionism as unique is wrong-headed, but not in itself antisemitic. All of these forms of anti-Zionism can be used as fig-leaves for antisemitism or be used to feed antisemitism, but they are not themselves antisemitic. [Editor: And I would add one more. Islamist anti-Zionism that is based on the idea that "Palestine" is Islamic territory that for theological reasons may not be governed by non-Muslims is not, by itself, anti-Semitic.]
Unfortunately, it’s increasingly the case that even those who approach anti-Zionism from one or more of these perspectives are at best tolerant of the anti-Semitism indulged in by some of their allies, and at worst engage in rhetoric that smacks of classical anti-Jewish themes, even if the individuals in question are not themselves anti-Semitic.
As I’ve noted before, there are two basic reasons for this phenomenon. The first is that given longstanding Western cultural prejudices against Jews, marrying anti-Zionism with anti-Semitism can be extremely effective from a rhetorical perspective. And, second, if you are inclined to believe that Israel and its policies are an especially grave danger to world peace and security you will tend to err on the side of being tolerant of anti-Semitism to the extent that you think it is furthering the anti-Israel cause [update: because you see Israel as a greater threat/danger/cause for concern than anti-Semitism]. Neither of these explanations are excuses, of course.