"Criticizing Israel is antisemitic."
Their strongest version
Antisemitism is real, rising, and sometimes disguises itself as anti-Zionism; Jews worldwide have been attacked over Israel's actions.
The response
Start where you agree, and mean it: antisemitism is real, evil, and rising, and any pro-Palestinian who traffics in it betrays the cause and its victims. Precisely because the charge is serious, it can't be spent as a shield for a state's policies. States are criticized; that's what states are for. The distinction has been drawn by Jewish scholars themselves — the Jerusalem Declaration on Antisemitism, authored by leading scholars of antisemitism, states plainly that criticism of Israel, even harsh, and support for Palestinian rights are not in themselves antisemitic. Israeli human rights groups (B'Tselem), Jewish-led organizations (JVP, IfNotNow), and Holocaust scholars (Omer Bartov, Amos Goldberg) make the same critiques. The test is simple: does the statement target Jews as Jews, use antisemitic tropes, or hold Jews collectively responsible for Israel? Then it's antisemitism — call it out, including on your own side. Does it criticize a government's documented conduct? Then the accusation is being used to end an argument someone was losing.