David M. Korn has written a lengthy, and I do mean lengthy, piece on Disney's Song of the South for Film Threat. His gist is that the movie is undeserving of its label as a racist animated flick. Other films, he reasons, which have misrepresented the plight of blacks during the slave era and The Reconstruction such as Gone with the Wind and (especially) The Birth of a Nation can still be purchased and viewed today, as opposed to Song of the South, which has not been seen, or been available, since a brief re-release in 1986.
Korn blames Disney and what he cites as an unwillingness to stand up for its creations. Recent examples of this include a lyric from the opening song in Aladdinthat was removed for suggesting Arabs enjoy throat-slitting (of course, they kept the scene where a shopkeeper threatens to chop off Jasmine's hand, but nevermind). The Lion King was also meticulously crafted so as not to be offensive to the African continent.