The Russians had an anti-Jewish history before communism.
During Communism, the regime rejected racism against Jews (and had many Jewish leaders), but was opposed to the Jewish religion and Zionism.
Stalin purged many Jews, however, he purged them not for being Jewish, but for other reasons. He also kept some Jews in his regime. He also purged many people who weren't Jewish. I think the term radical marxist would describe Stalin, more than anti-semite.
