Zionism in its purest form is the indigenous connection Jews have to Israel. You are correct that not all criticism of Israel is anti-semitic. And I agree that we need to have a serious discussion about Israel and the Palestinians creating a Palestinian state. But when criticism of Israel dismisses and denies the Jewish connection to Israel and essentially (even by implication) is saying Jews in Israel are illegitimately there, the line to anti-Semitism is pretty short.