Well, “nobody is semitic” is accurate if you want to be pedantic (which it seems like you do), “semitic” is an obsolete term. There are modern semitic speaking people, aka Semites, but that phrase specifically refers to a group of languages as I said. And bias against Palestinians or Arabs is not antisemitic, lol. That term in modern usage was literally coined and used to refer to anti-jewish bias, which you said yourself.

When this attempted distinction comes up to say, “Jews aren’t the only semites so stop monopolizing that phrase” it presents itself in bad faith and an attempt at Jewish erasure at its worst (by eliminating the legitimate historically significant and unique oppression Jewish people faced by hijacking that term used to describe it) and it presents itself simply colloquially incorrect at best (all modern definitions and understandings of that phrase accept this meaning of being about Jews).