If you’re equating the Jewish people with zionism, or conflating being in favor of zionism as somehow being benevolent to the Jewish people as a whole, you are treating the Jewish people as a monolith and are yourself being anti-semitic. Zionism is perfectly compatible with anti-semitism (see for example all those anti-semitic christians who enthusiastically support zionism), and anti-zionism is in itself not anti-semitic (cf Jewish voice for peace).
So making “zionist” a slur has nothing, absolutely nothing to do with being anti-anti-semitic or not.
Fair enough, all good. I’m leaving mine up because I think the point about the conflation of anti-zionism and anti-semitism being in itself antisemitic bears repeating.