I always think these arguments are so silly. Gone with the Wind is not a poltical novel, the movie is not a documentary.
There are good, strong black characters and weak and venal white characters, and vice versa. Scarlett is a "bitch heroine" in the mode of Becky Sharpe, THAT is a modern aspect and I'd think feminists everywhere would applaud Scarlett as a strong, if often ruthless woman. But it really is just a story for diversion, I'd be surprised if Mrs. Mitchel had more than that in mind. If she did, I'm afraid her work disappoints.
It is an historical romance, no more. I think it is a good novel and a great movie, but it is not a work of scholarship or history. Sincerely, only a moron would think that it is.