As they say, a stopped clock is right twice a day. Even people who are considered to be pariah have the chance to say something right. Doesn't meet you can't acknowledge that or give them a pass for everything else they have done wrong.

Its just an acknowledgement of fact and we should always be willing to give credit IF it is due. Not saying Marx is due that here, but we should not discount people completely because they happen to acknowledge a truth we don't like. That just makes us Progressives.