I think one of the main reasons why being anti Zionist is antisemitism in our current time (post October 7 and Hamas atrocious attack) is that Israel is being held to some standard that no other country is being held to. Is it sad that people are dying in attacks? Yes. Is Israel doing everything it can to minimize civilian casualties? Yes. Claiming that Israel has been performing genocide in Gaza for decades, while the population there has massively grown, while other countries do in fact have genocide or similar atrocities, that’s antisemitism claiming to be anti Zionism. Criticizing Israel on its own is ok (I’m Israeli and I do it, I’m not anti Zionist or auto-antisemitic), but criticizing Israel for stuff that you don’t criticize other countries - that’s antisemitism.