If you believe "Israel should not exist", you have to account for what would happen if it didn't. What would happen to the Jews who live in the Hamas-controlled "multicultural, multi-ethnic state" that would inevitably replace it? We all know the answer: they'd be killed. That's why people who call for the non-existence of Israel (anti-Zionists) are considered anti-semitic. If you support a position that leads inevitably to the death or displacement of millions of Jews, you are an anti-semite.