There's a pretty big moral space between advocating the overthrow of a government and the behavior of a Stalin or Pol Pot. Marx belongs to the former category, not the latter. But because of events that happened decades after his death, he's remembered as something he wasn't. His crime was being wrong, not evil.

Yes, and he was imprisoned for it. But what made Mandela great is that he changed and became a reconciliation figure.

The young MK starter and ANCYL member did not deserve a Nobel Peace Prize. But the Mandela in 1991 did.