Zionism is the idea that Jews should have a homeland in what is (now) Israel. It is not exclusionary - there are non-Jewish (including Muslim) citizens in Israel, and they have full rights (far more than they would have in most of the neighboring Arab countries, and yes there is sometimes racism - just like everywhere else in the world, though that is no excuse - but the that has nothing to do with Zionism).

You can choose not to support Zionism. But if you actively believe "Jews should not have a homeland" that is anti-semetic.