And, for the record, I'm not saying that Marx is completely wrong.  All important figures who wrote on social sciences were at least partly wrong.  All models are wrong, because they're generalizations.  The question is, "Did this person pick up on some characteristic of people that other had missed?  Did he or she articulate it better than others had before?"  If the answer is "Yes" to either of those questions, then I think it's worthy of being mentioned as an important contribution.  I can hate Karl Marx, and I can disagree with 99% of what he wrote, but I can still hold those opinions while recognizing that much of what he had to say was important, though I think it's generally accepted today that his ideas have proved more important to sociology than economics, in the long run.

Be nice to America. Or we'll bring democracy to your country.