It is a professional ambition of mine to one day do work at the Yale Initiative for the Interdisciplinary Study of Anti-Semitism, which is one of the leading ferments for cutting edge work on this particular form of invidious prejudice. One paper hosted by their site, by British academic and Engage heavyweight David Hirsch, gives one the better overviews on the linkages between anti-Zionism and anti-Semitism. I highly recommend it.
One of the questions which has engaged me for quite some time is this "why Israel" question. Why is anti-Zionism -- defined as the opposition to the idea and existence of Israel as a Jewish state -- the focus of so much seemingly disproportionate attention and hatred by those who claim to part of the broadly-defined "left"?
Several answers present themselves. The first is simply that the speakers are motivated by anti-Semitism. That might be true for some, but I highly doubt it is true for all. Hirsch very clearly disclaims that he is not inquiring as to what various "critics" or condemners have inside their heads, and I agree that I simply have no way of knowing the state of mind of these persons. I also agree with Hirsch that this is in many ways an irrelevant question: Whether or not someone conceptualizes themselves as a hater of the Jewish people matters quite little if their actual words and actions act to perpetuate anti-Semitic subordination.
Hirsch implies that part of the answer lies in the continued failure of Marxist and socialist predictions as to the imminent collapse of the bourgeois capitalist system, and the need for an explanation. Since there is a deep well of anti-Jewish literature which is predicated on the ability of Jews to control the world through, inter alia, the financial, media, and entertainment industries, the continued existence of capitalist structures can best be explained by the transcendental and ahistoric power of these Jewish institutions who seem to operate unconstrained by the rules of time and space (much less morality). I don't know enough about Marxist political behavior to evaluate this statement, but as a general description it seems reasonable enough: If X "has to happen", and X persistently refuses to happen, the temptation to resort to conspiracy-mongering in order to explain why X isn't occurring must be mighty tempting.
Nonetheless, a large part of me suspects that the answer is much more simple: Extreme opposition to Zionism is the path of least resistance for a substantial portion of relatively marginalized "progressive" ambitions. Least defensible is the desire for a psychological balm for the wounds of Western colonial and imperialist endeavors. Even assuming Israel is reasonably associated with these practices (which I don't believe, but am putting aside for now), the motives of the critics are far from pure. Seeking guilt release for these actions, but not wanting to threaten the privileges and benefits they maintain from the outcroppings of these endeavors, leftists find that attacking Israel brings with it all the self-righteousness of being an "anti-imperialist" without seriously threatening the benefits the speakers get from the status quo. As Shulamit Volkov put it, Anti-Semitism is a "convenient way of attacking the existing order without demanding its total overthrow and without having to offer a comprehensive alternative." Put simply, while anti-Zionist ideology is couched as being resistance to the Western program and thus (when advanced by Western academics) selfless moral sacrifice, if Israel was destroyed, the social position of the Western academics and speakers who propounded the policies would not change in the least. All the rewards, none of the risks.
But many leftists will say that the various political ideologies which they claim motivate their anti-Zionism are quite genuine -- not simply a way to disassociate themselves from "bad" Western acts. And perhaps I believe them. And there is a reasonable account for why such persons focus so much of their energy on Israel compared to other institutions which seem equally or more violative of their political commitments. Simply put it: It's a battle they feel they can win.
Suppose you oppose the entire idea of nation-states -- or, to go further, states in general. Unfortunately for you, you're part of a rather fringe minority, and one whose political program appears rather distant: China does not seem to be going anywhere. By and large, the notion of the "state" seems pretty well entrenched in the international system.
Israel, however, is not so entrenched. China is huge, Israel is rather small. China has broadly accepted social legitimacy, Israel does not. There is no political constituency to abolish China, there is a large political constituency advocating the abolishment of Israel. Leftists thirsting for a reachable victory understandably see Israel as their best shot. If all the people working to destroy Israel just lock arms and push, they might manage to bring down at least this part of the modernist edifice.
The problem, though, is that these leftists don't sufficiently analyze why Israel is so vulnerable. Happily locking arms, they don't bother to look and see who is on their left and right. As it turns out, Israel is vulnerable because it is the target of several massively reactionary organizations whose stated political agenda is the subjugation (if not extermination) of the Jewish people, combined with the fact that this agenda is not considered to be of major concern to their Western allies. The relationship is symbiotic: Israel is vulnerable because those who wish to kill Jews know that "anti-Zionism" is a rallying flag from which they can gain international support -- even if the supporters of the latter don't see themselves (and would actively disclaim) that they personally wish to see harm to the Jews.
When Hamas lobs a rocket into Ashkelon, their leftist supporters say they are "resisting occupation". Perhaps so. But firing rockets also and equally forwards Hamas' agenda of slaughtering Jews. One cannot sever these two ambitions (supporting one but not the other) when the same act so clearly advances both causes. By locking arms with Hamas, one is complicit in the world they wish to construct after the collectivity succeeds in bringing Israel down.
To be sure, there is significant cognitive dissonance that occurs in the leftist mind when the motive for political action is predicated on the peculiar vulnerability of a marginalized group. Hence, the effort at casting the Jews as hyper-powerful. By constructing the Jew as an entity that is inherently empowered, leftists can avoid the implication that they are merely preying on the weak. Alternatively, they represent Israel is the epitome of modern evil -- exceeding that of, say, China, Sudan, Zimbabwe, North Korea, or Russia -- which is the true motivation of the disproportionate backlash (not that many social actors see attacking Jews as legitimate in a way that attacking other social groups is not). Notwithstanding the psychological usefulness of this maneuver, it still represents a fundamental sublimation of the actual status of Jews worldwide, and likely position of Jewish communities in the event that social program aided by these leftists comes to pass.
None of these defenses require that we think that leftists actively seek out harm for Jews, though they do imply that they are somewhat indifferent to it or at least are willing to gamble recklessly with Jewish lives. The leftist motivations here do not stem, in other words, from the personal anti-Semitism of the authors. But I am not interested in the whether or not these persons are good at heart, and both the upshot of their political machinations and the political tactics the use to achieve their ends have vicious implications for the legal, political, and social equality (not to mention security) of Jews. That's enough to make the question of anti-Semitism salient.