Genetically similar, but that means nothing. Croats, Serbs and so-called Bosinaks are of the same ethnic group.
So then you would feel comfortable labeling them as "anti-slavic"?
You’re wrong, though it puzzles me why this is such an issue.
You said, “Besides, I happen to have studied history,…”. Pull out your history books and read them. Or do a google search (try Wilhelm Marr & anti-semite). You will discover that the term “anti-semite” has nothing to do with race. Wilhelm need to coin a friendlier word than Judenhass (Jew-hatred, even sounded evil in German) for his political beliefs. He thought anti-semite sounded snappy, and named his political party the Anit-Semite Party, its objective the expulsion of Jews from western Europe. The term is correctly applied historically for hatred of Jews, but never refers to hatred of “semites”..
Your argument is often used in the Arab world as cover for anit-semitic statements. The idea is to turn the argument, discuss semitic rather than Jedenhass. It is improper usage of the word.