Etymology <> meaning. It doesn't matter what the individual parts of a compound word "mean". It doesn't matter what language they came from, or what they meant in that language. What matters is how a language community uses the word. The word "antisemitic" is used by speakers of English to mean "prejudice, hatred, violence (etc) against Jews." It doesn't matter a rat's ass that Arabic is called a "Semitic" language. What matters is how the vast majority of the speakers of English use the word "antisemitic." That's what it means for a word to "mean" something. Usage. Not etymology.

You might as well say I don't wear "glasses" because the lenses are made of plastic. Totally misses the point.