A virus like any other, anti-Semitism is subject to infinite mutations, the better to adapt to changing immunological conditions. Before World War II, it was a industrial-financial hold that the Jews were said to possess over world affairs. Hidden behind the scenes of governments and media organs, Jews were credited with starting and ending wars, making capital markets rise and fall on a whim, and generally wielding the reins of that colicky beast known as History. They weren't out front because they were (rightly) reviled and persecuted. That they operated in the shadows and out of some secret playbook made them even more sinister.
Then, Israel was founded and the paranoids were given a concrete target, one circumscribed by contiguous borders and heavily endowed by a guilty Western establishment.
Sure, anti-Zionism was a legitimate movement not necessarily run by anti-Semites — in 1948. A lot of anti-Zionists then were themselves Jews, not even on nodding terms with "self-hatred," who simply couldn't see the point in a official homeland when a de facto one had already presented itself in the diaspora haven of America.
That was then, this is now.
If you're looking to distinguish between a long-held opposition to Israel on pragmatic grounds and a pathological antipathy against Jews, you might ask yourself the following: Do Zionists still exist? What happens to a movement once its goals have been attained? Those who continue to agitate beyond a pre-determined objective have either shifted the goalposts (and will probably keep on shifting them) or are closet utopians who never actually believed what they claimed to. They keep coming up empty, no matter how successful they are.
To be "anti-Zionist" at this point in history is to be selectively anarchistic; selectively because you want the end of one state and one state only. Why might that be? If it was purely out of concern for the past and present turmoil of the Palestinians, we might wonder, haven't historical injustices precipitated the founding of every modern nation? And haven't they been correctable by reform, not total annihilation? Why should one state be singled out for the rough treatment?
Here is Matthias Küntzel:
Just as Hitler sought to "liberate" humanity by murdering the Jews, so Ahmadinejad believes he can "liberate" humanity by eradicating Israel. The deniers' conference as an instrument for propagating this project is intimately linked to the nuclear program as an instrument for realizing it. Five years ago, in December 2001, former Iranian president Hashemi Rafsanjani first boasted that "the use of even one nuclear bomb inside Israel will destroy everything," whereas the damage to the Islamic world of a potential retaliatory nuclear attack could be limited: "It is not irrational to contemplate such an eventuality." While the Islamic world could sacrifice hundreds of thousands of "martyrs" in an Israeli retaliatory strike without disappearing–so goes Rafsanjani's argument–Israel would be history after the first bomb.
[…]Obviously, from a logical point of view, enthusiasm for the Holocaust is incompatible with its denial. Logic, however, is beside the point. Anti-Semitism is built upon an emotional infrastructure that substitutes for reason an ephemeral combination of mutually exclusive attributions, all arising from hatred of everything Jewish. As a result, many contradictory anti-Jewish interpretations of the Holocaust can be deployed simultaneously: (1) the extermination of millions was a good thing; (2) the extermination of millions was a Zionist fabrication; (3) the Holocaust resulted from a Jewish conspiracy against Germany that Hitler thwarted and punished; (4) the Holocaust was a joint enterprise of the Zionists and Nazis; (5) the Zionists' "Holocaust industry" exaggerates the murder of the Jews for self-interested reasons; (6) Israeli actions against the Palestinians are the "true" Holocaust–and so on.