I guess it depends on what the meaning of "the human basis of his religion" is. What does that phrase mean? If "the human basis" of the Jewish religion is corrupt, isn't that the same thing as saying Judaism is corrupt?Here is what you don't understand. Marx at this point in his development based most of his thinking about religion on Feuerbach, another left Hegelian. One of Feuerbach's principal theses was simply that every statement we made about God was really an inverted claim about our own social lives--religion was not about heaven, but an expression of the human condition (or "human basis"). Yes. Marx believed Judaism was corrupt; but he believed all religion was corrupt. He never advocated the liquidation of the Jews.
He said eliminating Judaism was more important than eliminating Christianity. Hitler merely took it one step further, and eliminated Judaism by wiping out everyone who was of the ethnic group associated with Judaism. He did so for the same reasons--he believed Jews were oppressors, and that they would poison society, just as Marx believed. He just took a more drastic approach to eliminating Judiasm.