I suppose it means that you don't have to be a good guy to bring about positive change. Apartheid is gone, and that is a good thing, but I have issues with crediting the wrong ideologies for it.
He was no less a good guy than George Washington, who also took up armed struggle against tyranny (which included instances of tar-and-feathering (as opposed to the flaming necklace) and other unsanctioned violent attacks on authority, which is in the nature of armed resistance) and eventually led a new nation that rose out of it. Unlike Washington, however, Mandela eventually sought to forgive and work closely with those who had oppressed him to ultimately lead a peaceful transition to a one-person, one-vote democracy. Your distaste for his embrace of Communism notwithstanding (which only came after "champions for Democracy" such as the U.S. and the U.K. refused to support the majority of South Africans' fight for Democracy against the most anti-democratic regime of the 20th Century), I'm sure he found accepting support from the Soviet bloc more palatable than going along with Apartheid, an utterly indefensible system of government (based in part on the so-called religious concept of Predestination) more vile than anything dreamt up in the halls of the Kremlin. When forced to choose between the two, the choice is plainly obvious.
Show me a perfect man and I'll show you a fantasy. If your standards for acknowledging heroism require that the person not have committed any transgressions along the way, then no one who has ever lived has yet to meet those standards. Madiba came closer than any of his contemporaries among world leaders. I am thankful for the work he did while he was with us.