Well, I think the conflation of anti-Zionism with anti-Semitism is a very different thing than almost every other mistaken cry of anti-Semitism. Things like decrying "The Passion" (and AGAIN, because I'm loathe to defend something I haven't seen, I'll just say this is all "from what I've read") and (since I just saw Auto-Focus last night) the anger/criticism that accompanied the beginning of "Hogan's Heros" are pretty meritless. I think the general argument there is whether or not such oversensitivity is justified; I mean, in the 1950s, I'd have a hard time coming down hard on a Jewish organization worried about positive portrayals of Nazis.
Anti-Zionism, however, is rooted in anti-Semitism, and could not exist without the soil of anti-Semitism. That doesn't mean every anti-Zionist expression is anti-Semitic. But it's like a white good ol' boy police force in the old South. Most of you will string up (or at least legally send up the river) a Negro without a second thought. Maybe there are a couple of you who really try to overcome the instutitional and cultural racism you've grown up with, and do a generally good job. In the end, you know, the department did convict a lot of genuinely guilty black folks, but in the scope of history, it's hard to give much moral credence to those convictions, because you've effected them in such an impossibly inobjective atmosphere.
Sure, the anti-Zionist movement's excuse is that Israel HAS actually done bad things. But even the worst anti-Semitisms throughout history (represented by expulsions of Jews from Spain, Protocols of the Elders of Zion, etc.) were not entirely based on fiction. The core of institutional anti-Semitism--including anti-Zionism--is the treatment of the crimes of Jews as worse than the crimes of everyone else, singling them out for special prosecution. And that is exactly--exactly--the anti-Zionist flaw. Israel's crimes are regularly focused on and called "worst ever" when every other state--including the Arab states around Israel, and Palestine itself--do equal or much worse.
(My personal opinion is that a lot of people have been fooled into calling themselves "anti-Zionist" without understanding exactly what that connotes. Because of Israel's militarism, I very strongly condemn a lot of its policies, probably equally to many who call themselves anti-Zionists, and I would never call myself an anti-Zionist)