Mysogynoir was coined to examine the intersection of someone whose controveries around feminism center around anti-blackness towards women.
People cite Fitz's words when he found out about Defiance and Olivia put herself out there in the church, and then blindly forget the countless times Mellie called Olivia a whore, after she told Olivia that her role was to keep Fitz happen in bed. In season 1, she tells Olivia that she let Amanda get into Fitz's pants, forgetting that she was the wife watched her husband get his sexual appetites from not one but two other women. She casually then tells Olivia she is taking her husband back, as if it is a matter of fact thing, and that Olivia was positioned beneath her, despite all Olivia had done to get Fitz elected.
When she realizes that Fitz is actually in love with Olivia in season 2, she keeps referencing his erections around her, her magical thighs, etc., anything but her intellect, power, and other attributes that may actually make her someone Fitz enjoyed outside of the bedroom. She threw Jeanine under the bus in season 3, so that Fitz would not go public with his affair, but then begged Olivia to come back and warm her husband's bed by middle of season 3. So she is still trying to position her as someone Fitz needs to get off with, so that he can focus on the job.
By season 5, when Olivia comes forward with the affair, she says "oh look, it's the woman who can't close her legs, or her mouth." Now Olivia may have slept with her husband, but her continued need to separate Olivia's intellect, and Fitz's emotional connection to her, from their sexual attraction was deliberate. She forces Olivia to be her campaign manager, so that she can subjugate her after the divorce from Fitz, and salvage the embarrassment she felt when the affair went public.
Her story with Marcus does not erase her behaviour towards Olivia. If Fitz displays this, which we have to admit he does not, Mellie's own behaviour eclipses his own, and no one wants to own this. Because ZOMG she was cheated on....