Yes, he was. I don't know why people attempt to deny this. Marx is not my buddy nor was he a prophet.

But Marx was a jew!

Marx did not view himself as a jew.

He certainly was not among the buffoons like Bakunin or Proudhon that believed the jews controlled the world and pulled the strings.

To Marx judaism expressed the material world of commodity exchange. On the Jewish Question and Capital I are filled with quotes holding such a view of the jews. Whether he thinks this was bad or corresponding the superestructure of capitalist society are 2 different things.

I would argue that he had a personal dislike for jews. The obscure letter he sent to Engels is well known. Referring to Ferdinand Lassalle as a "jewish n-word" and making observations about the shape of his skull and head, and that the mixing of Germanness, jewishness with "basic n-word stock" gives rise to a peculiar product.