Anti-Zionism is not antisemitic and antisemitism is not anti-Zionist. Historically the German far-right was actually indifferent to Zionism because it provided a way to get rid of Jewish people domestically. They placed restrictions on emigration to prevent wealth drain (i.e. rich Jewish people taking their money/property with them when leaving Germany) but the only reason they shut down the Zionist emigration project was that they invaded Poland and suspended all legal migration because of the war.
There is a line between being pro-Palestine/anti-Israel and being antisemitic. That line is when you insist on people being evicted from Palestine/Israel simply for being Jewish. Yes, some protests have seen people cross that line and some groups who have organized protests were firmly on the wrong end of that line. But the narrative that you can't be anti-Zionist without being antisemtic or that you can't be opposed to Israel's government's action without being opposed to the existence of Jewish people in Palestine/Israel is in itself antisemitic by deliberately conflating a state with individuals, many of whom don't even live in that state nor agree with it.
There have been many Jewish opponents to Zionism and Zionism in Palestine especially since the inception of the modern Zionist movements. Until the state of Israel was created there was a strong divide between Jewish Zionists and Bundists, the latter arguing for a stateless nationhood. Bundists and other Jewish anti-Zionists still exist, they're just relegated to obscurity because Israel dominates the international conversation and most Jewish interest groups have aligned themselves with Israel for pragmatic reasons.
Also, finally, Israel's current government as well as the illegal settlers in the West Bank (and prominent figures who fantasize about a "Greater Israel" including at least all of Palestine but potentially also parts of the surrounding countries) are in fact most accurately described as "far-right conservatives" as well.