A chunk of it is scapegoating Israeli Jews for their own sense of guilt. It’s easy to dehumanize Jews, the world at large has quite a bit of practice. People who live on colonized lands or who live in countries that have benefitted from colonialism honestly need to consider the circumstances of indigenous people where they live now or who they have exploited. They also need to consider that a large chunk of the reason Israel exists in the first place is because their countries kicked their Jews out, oppressed them, and/or murdered them en masse. If your country did any of that, criticizing Jews who fled to the only country that would take them in takes a lot of chutzpah. But of course those countries do so because they’d rather feel that the Jews deserved what happened to them rather than take any accountability for helping to create the current situation. If your country is presently unsafe for Jews *cough* France, Belgium, Ukraine, Turkey, South Africa *cough* ask yourself, if you are against Israel’s Right To Exist, why the hell are you giving legitimacy to Theodor Herzl’s case? A world without an Israel needs to be a world free of anti-semitism, otherwise these people are advancing the cause of anti-semitism, and that needs to stop.
So much of the “Israel shouldn’t exist” rhetoric is ultimately useless, anyway. Israel does exist. Its creation displaced hundreds of thousands of people. These are the issues that need to be addressed. Annihilationist rhetoric is divisive and pushes away from the core issue which is, one way or the other, Israeli Jews and Palestinians need to be able to find a way to live together as neighbors. That is the real problem. How do we get there?