Although Arabic is a Semitic language, just like Hebrew, antisemitism is used to refer specifically to hatred of Jews. This is an accident of history and has no deeper meaning.
Briefly: in the mid-1800s, due to the Enlightenment, religious bigotry was falling out of favor in many elite circles as science’s star rose. The bigots, minds unchanged but seeing the way the winds were blowing, took shelter by claiming that they hated .
for scientific reasons. By allegedly focusing on differences between races, the bigots gave a scientific veneer to their sordid hatreds. They even founded a now-disgraced field called Eugenics, claiming to study scientifically these alleged racial differences. The phrase anti-Semitism emerged as a part of this shift; a particular Christian anti-Jewish bigot wanted to pretend that he was merely a scientific racialist. He did this by discussing the supposed “Semitic race”, and a Jewish philosopher called out this deception for what it was, coining the term.
For the record, Eugenics was both evil and bad science. Whatever the flavor of the century is, wherever they’re from, the bigots haven’t changed anything below the surface.
But would Hitler have eventually turned on anyone and everyone, including Arabs? Without a doubt. Despite his genuinely-held bigoted beliefs, Hitler generally focused on one issue at a time, as described in the haunting poem, First They Came:
They came first for the Communists, and I didn’t speak up because I wasn’t a Communist.
Then they came for the Jews, and I didn’t speak up because I wasn’t a Jew.
Then they came for the trade unionists, and I didn’t speak up because I wasn’t a trade unionist.
Then they came for the Catholics, and I didn’t speak up because I was a Protestant.
Then they came for me, and by that time no one was left to speak up.