The fact that they use “antisemitism” in this case shows you how they use that label as a weapon.
The Palestinians are a semitic people. What’s more anti-Semitic than committing genocide on Semitic people?
That’s because they rely on the work of some 19th century German pseudoscientist that designated European Jews as the “Semitic” people. And from there you get this modern iteration of “Antisemitism” which doesn’t take into account other Semitic peoples.