I agree with most feminists that getting out the message that "No means no" is of vital importance for preventing sexual assault. And that's is why it's critical that both options exist -- yes as well as no -- in a meaningful way.The problem of not being able to say yes when you want to leads to other problems. For example, Utah has a high rate of teen pregnancies. This isn't terribly surprising to me. The urge to have sex is just too strong to resist for some people. But in a religious culture where extra-marital sex is a sin only slightly less severe than murder it isn't really an option to consciously prepare to have sex. For example, why would a good Mormon boy go out and buy condoms? That would be admitting that you are not only willing to fall, but you're also prepared. How's that going to look to your Bishop, Stake President, and General Authority that are going to have to interview you before you go out on your mission? The very fact that you had condoms is an admission that it wasn't just that things got out of hand and you slipped; it's an admission that you started making out with the premeditated intention of going all the way. It's the Mormon equivalent to the difference between premeditated, first-degree murder and manslaughter. The same thing would apply, I guess, to a good Mormon girl who went on the pill. In the end, safe sex winds up being dangerous to your soul if you are a Mormon because it's the moral equivalent to being a cold-blooded killer instead of just a reckless youth. So, even though good Mormon kids really, really want to have sex, they have to say that they don't and act accordingly right up to the moment when they do. Then they have to deal with the shameful consequences and humiliation and guilt that their culture inflicts on them.
In a repressive society, some women want sex. Yet no women are allowed to want sex. So you get a situation where the women who really mean no say no and the women who don't mean no also say no.
Note, I still think no means no and should be respected. I'm just pointing out why in some cultures people may say no when they really mean yes or at least wouldn't mind saying yes.