Film studios are not in the business of historic preservation, as the 2008 Universal fire attests. They are in the business of providing entertainment. If a film like Song of the South does not speak to contemporary tastes, it will be kept out of circulation. If thirty seconds need to be cut in order for the film to speak to contemporary tastes, then those thirty seconds get cut. This falls within the studio's rights. I don't necessarily like it either, but that's the reality.