Even the word antisemitism seems to have been hijacked to purely mean being against a particular religious belief system.
The word anti-Semitism was not "hijacked." The word was created specifically to refer to Jews.
The term “antisemitism” was not originally a generic label for hostility toward a religion, nor was it “hijacked” from some broader neutral meaning. It was coined in German in the late nineteenth century specifically to denote hostility toward Jews. The word is generally traced to Wilhelm Marr, a German publicist, who used Antisemitismus in 1879 as part of a political campaign against Jews in central Europe. The point of the new term was to give Jew-hatred a more modern, pseudo-scientific, racial-sounding label than the older blunt expression Judenhass (“hatred of Jews”).
That matters because the term emerged in an era when many European ideologues wanted to recast anti-Jewish prejudice as something more respectable than old religious bigotry. Instead of saying, in effect, “we hate Jews,” they framed Jews as a permanent alien “Semitic” people supposedly in conflict with “Aryans” or Europeans. So the word antisemitism was born not as an objective scholarly category, but as a propaganda term with a racist veneer.
Historically, hostility to Jews long predates that word. In earlier periods it was usually expressed as religious anti-Judaism: Jews were attacked for rejecting Christianity, accused of deicide, or targeted through medieval myths like blood libel. By the nineteenth century, however, a newer form developed that treated Jews not merely as adherents of a religion, but as an allegedly unchangeable race or people. The coinage antisemitism belongs to that transition.
The word was invented to mean hostility toward Jews. It did not originally mean opposition to religion in general, nor opposition to all “Semitic” peoples. In actual historical usage, it referred to anti-Jewish animus from the start. The spelling “antisemitism” is often preferred today over “anti-Semitism” precisely because the latter can misleadingly suggest a connection to “Semites” as a broad linguistic category, whereas the historical term was always aimed at Jews.