Never saw this since it's out of print and considered too racist. Just watching it on YouTube now to form my own opinion.
Br'er Rabbit who represents a black man is caught by a Fox who represents a white man when Br're is noosed and hanging. Scenes like that is why the film is considered racist.
After seeing Zootopia I was curious in this since Zootopia which is against racism is supposed to be pretty much the opposite of Song of the South.
If you don't spend too much time thinking about what makes it racist; the film is light-hearted and still a classic. The biggest problem with it though is that it makes it appear black people were perfectly happy as slaves.