Anti-zionism isn’t exactly the same thing as antisemitism, but it is almost always an expression of antisemitism. I have thought hard about this, and I can think of only three non-antisemitic grounds on which one can oppose zionism. Anyone who is anti-zionist on any grounds except these is an antisemite. The problem is that all three are even stronger grounds for opposing the “Palestinian” cause. I cannot think of any way at all to oppose zionism and support the “Palestinians” without being an antisemite.
The three non-antisemitic grounds I have identified for opposing zionism are:
1. Anarchism. If you oppose the existence of all states, then of course you will oppose the existence of Israel or of a hypothetical “Palestine”.
2. Pacifism. If you believe violence is always wrong, even in self-defense, then you will oppose the IDF’s existence and everything it does to defend the Jews, just as you will oppose the “Palestinian” efforts to destroy Israel.
3. Torah. If you believe that G-d send the Jews into exile and they must remain there until He frees them, then zionism is like a prison breakout. A prisoner does not lose title to his home, it still belongs to him and nobody else has the right to live there without his permission, but he has no right to go there. He can have a lawyer evict squatters, but he must remain in prison. Thus if you believe this you will oppose zionism, but you will oppose even more strongly any attempt to steal the Jewish land while its owners are away.