The letter seems to be fitting into a pattern of pro-Israel organizations, such as Canary Mission and Betar, targeting critics of Israel’s military actions, as well as supporters of Palestinian self-determination. Betar says it has provided lists of noncitizen protesters to Immigration and Customs Enforcement, the Department of Homeland Security, and other government agencies, recommending deportation.
Anti-zionism is not Antisemitism. Your conflation of the two is genuinely antisemitic.
Zionism is anti-Semitic at it’s core, it other-izes Jewish people, and justifies the violent settler colonialim of Israel as in the defense of all Jewish people, which only serves to further fuel genuine Antisemitism at the expense of Jewish people globally. Zionism is also an inherently fascist ideology. The ethnic cleansing of the native people of Palestine has always been fundamental since it’s inception as a colonialist movement.