Its well known that when he joined the Nation of Islam, he held racist views against white people, however, he came to rescind these views later after Elijah Muhammad died. He stated in his autobiography that one of his biggest regrets was turning his back on Malcolm X after he had abandoned the racist NOI and later came to the realisation that racial hate was wrong, no matter who the colour of the one being hated or doing the hating was. So we can either eternally despise him for what he was, or respect him for what he became.
Muhammad Ali Backed Reagan and Many Other Republicans
http://www.newsmax.com/Newsfront/Muhammad-Ali-Reagan-Repubicans/2016/06/04/id/732336/#ixzz4Ajl2283l