From a family perspective. A Yid is a Yid no matter what he converts to. You know that, I know that. Family is family no matter how much you try to distance yourself from those family members that are responsible the most egregious of acts.
Whether that man comes from a long line of rabbis or a long line of Christian scholars doesn’t matter. What I am trying to point out to you is that Marx came from a well to do family with the lineage to back it up. If your well to do family that has been a blessing to the local community for quite a long time do you think the descendant’s would want to claim a man responsible for the murders of 200+ million people to be a part of that family? I don’t think so!
Now why do you think the Ein Sof allowed Marx to be in the right place at the right time in history to do what he did?