I don't think it's all that offensive. I think Gone With the Wind is MORE offensive, IMHO. But then again, I'm a white guy, and not always the most sensitive one. So the filter through which I watch movies is not the same as everyone else's...
If memory serves the movie takes place right after the Civil War, but most of the former slaves are still working the fields. Either that or it's still pre-Civil War and black people ARE slaves. Of course, there have been plenty of movies featuring black people as slaves, but in Song of the South, the slaves usually seem pretty happy. Singing, dancing, it's great to be alive, our massa's so good to us, that kind of thing. For some people who experienced (or still experience) the struggle of being black in America, the idea of this group of people being SO happy to be subjugated is insulting.
Add to that the sterotypical "Negro" way of talking-it's even written in the song lyrics: "It's the truth, it's ac'chual, everything is satisfac'ual." You also have little Johnny's relationship with Uncle Remus. Some see it as a young boy looking up to, and wanting to spend time with, and older man with incredible stories to tell, and what's the harm of that? Others see it as a spoiled little white boy using an old black man as a toy, winding him up and being entertained by him and his stories. When he's pining for Uncle Remus, is it love and friendship? Or a spoiled brat not getting his way and being allowed to "keep" an old black man the way others might keep a pet?
And of course there's the stereotypical fat Mammy character, played by
Oscar winner Hattie MacDaniel.
The tone of the film by its end is one of tolerance and acceptance, IMHO. But getting there, there are elements that are not historically accurate, and in the eyes of some, minimize the plight of being black in America, and can't appreciate it's end moral because of it.
FWIW, I have a copy on VHS, bumped it up to DVD-R recently, and I'll be the first to buy a legit DVD if one is released. I'm sure that most of us on this forum own the Walt Disney Treasures DVDs, the sets that come in limited numbered tins. So I'm sure we've seen at least some of the cartoons that include an intro by Leonard Maltin warning people that the next cartoon may be considered offensive today, but will hopefully be understood in the context of the time in which it was made. What I HOPE is that they might do the same thing with SotS, give it an introduction that'll dilute the concerns of racism, so everyone that wants to own the movie can.
Even now, technically, ANYONE can own a copy, as long as you buy a legitimate copy from overseas first, then pay to have it transferred to an American NTSC format, VHS OR DVD, which is exactly what I did. It's more expensive than just, say, buying a bootleg, but it falls under the Fair Use Law and wouldn't get you in trouble either. If you make a copy for anyone else, or for sale, then you run a pretty big risk.
