But yeah, there is indeed some irony in the term "antisemitism" in the context you describe
The only erasure is the attempt to diffuse the term to include Akkadians, Amharics, Carthaginians, Phoenicians, Black Israelites, adherents to the Nation of Islam, all 1.3 billions Arabs, what-have-you, when it always and only ever referred to anti-Jew hatred.
(More broadly, "they're semites too" is the "Elon Musk is African American" of I/P discourse. You can recognize extraordinary human tragedy without re-using race science.)
(By comparison: nobody who isn’t a racist talks about Japhetites or Hamites, but these are the coextensive groups implied by the existence of Semites.)
I'm sorry for responding as though we were using the received definition, because we're now solidly in the "Elon Musk is African American" quadrant of stupid I/P meta-arguments.