From a red pill woman:
“My defense of monogamy was built on the idea that femininity is like a crop that only grows in a climate of committed sexual relationships: introduce casual sex to the environment, and the crop fails. This places an element of responsibility on men and society as a whole as the “farmers” of femininity.”
In other words, in addition to the plethora of male responsibilities, he is all responsible for growing her femininity. If he is not monogamous or has an affair he then causes her femininity to wilt. This is nonsense to me and almost a threat to men in that it implies “if you cheat, I won’t be feminine and its your fault”. However, I will say this fits nicely with the inverse red pill concept that women inspire masculinity. It is women who make men masculine. It is said that a woman has to first submit before he can be a man. Likewise, with this theory it sounds like a man has to be faithful in order for a woman to be feminine.
A side thought–I would think monogamy would be less likely to make women feminine. After all, don’t women tend to let themselves go after marriage under the thinking that “hey, I got him in the bag, he isn’t leaving me now, so why should I go out of my way to look nice”. On the other hand with any form of non-monogamy, she is in constant competition with other women and therefore motivated to always look and act her best.