Scarlett O'Hara was not beautiful, but men seldom realized it when caught by her charm as the Tarleton twins were. (1.1)
This is the first line of the novel, and it immediately equates femininity with deception or artificiality. Scarlett is not really beautiful, but she charms men into thinking she is. At the same time as it associates Scarlett with feminine duplicity, it also suggests she's not really feminine—and Scarlett not really being feminine is a major theme of the rest of the novel as well.
Scarlett wanted very much to be like her mother. The only difficulty was that by being just and truthful and tender and unselfish, one missed most of the joys of life, and certainly many beaux. (3.119)
For Scarlett, being like her mother is being feminine and ladylike. Scarlett aspires to be like that, but doesn't really like it. Femininity is kind of a drag.
There was no one to tell Scarlett that her own personality…was more attractive than any masquerade she might adopt. Had she been told, she would have been pleased but unbelieving. And the civilization of which she was a part would have been unbelieving too, for at no time, before or since, had so low a premium been placed on feminine naturalness. (4.56)
Mitchell is able to see that the South restricted white women, even if she can't see the way it restricted black people. Note too that the "low premium placed on feminine naturalness" here only applies to white women. Black women were not meant to be artificial, nor, for that matter, attractive. Scarlett flirts and flits, but Mammy is presented as utterly asexual.
Women knew that a land where men were contented, uncontradicted and safe in possession of unpunctured vanity was likely to be a very pleasant place for women to live. (8.78)
This seems really unconvincing. Women's lives are pleasant as long as they don't do anything like have opinions, or desires of their own that might displease their overlords? You might as well say that black people's lives were pleasant as long as they didn't try to stop being slaves—which of course is something that the novel thinks is true as well. Oops.
"And perhaps I'm staying here to rescue you if the siege does come. I've never rescued a maiden in distress […]."
"I won't need you to rescue me. I can take care of myself, thank you!"
"Don't say that, Scarlett! Think of it, if you like, but never, never say it to a man." (17.132-134)
Rhett's sentiments are echoed several times throughout the novel. Women (or white women) are only supposed to be attractive and enticing if they're helpless. The novel admires Scarlett to some degree, but the two loves of her life, Ashley and Rhett, are both really uncomfortable with her capability, and both arguably abandon her because of it. Go team.
[…] he felt the usual masculine indignation at the duplicity of women. Added to it was the usual masculine disillusionment at discovering that a woman has a brain. (36.19)
Frank sees women as duplicitous… but really it's his own sexism that makes him so easy to fool. He assumes that women don't have brains, and since women do have brains, he ends up looking like an idiot. Hard to pity him, really.
"He should have killed you rather than let you come up here—and to me, of all people! God in Heaven!" (36.194)
Rhett thinks Ashley should have killed Scarlett rather than letting her go to Atlanta to try to get money out of him. A real man kills a woman rather than see her marry or sleep with someone he doesn't want her to marry or sleep with. Rhett's not really a moral beacon, in case you hadn't noticed.
"Scarlett, the mere fact that you've made a success of your mill is an insult to every man who hasn't succeeded." (38.112)
Again, Margaret Mitchell was a very successful woman, just like Scarlett. The contempt for the envy and littleness of men here seems to come from the heart.
"Oh, dear, this is my only chance to know what a bad house looks like and now you are mean enough not to tell me!" (46.38)
Mrs. Meade, a virtuous woman, wants to know how bad women live. The novel says that this is true of all virtuous women. Upper-class white women in the South were supposed to be good and pure and above such things, but Mitchell suggests that the purity is artificial or enforced; women are as curious and interested in sex as men are. If you prevent them from talking about it, that doesn't make them less interested. Quite the contrary.
"Scarlett, understand this. If you and your bed still held any charms for me, no locks and no entreaties could keep me away. And I would have no sense of shame for anything I did, for I made a bargain with you…" (51.44)
This is a straightforward argument for marital rape. Rhett says he married Scarlett, so he should be allowed to have sex with her whenever he wants, and feels entitled to rape her whenever he will. This is supposed to make him seem dangerous and worldly, but we're not fooled.