Think about it. The redpill basically states that women have their sexual goals and preferences. These goals and preferences are not derivative from the male ones, but something else entirely, defined by the different biological role of women. These preferences are not up to debate, in order to get a woman you have to study these preferences and then improve yourself to match women's standards. It also has cynical and manipulative tactics, but women were using theirs since the dawn of time, they just didn't need redpill to share them.

On the other hand pro-women groups basically deny men the right to have any preference they usually have:

He wants his woman to be thin? He's fat shaming!

He wants her to have low n-count? - He's slut shaming!

He wants her to be younger? He's creepy or "pedo" (for dating a legal age woman)

He wants her to be good at housekeeping? He's patriarchal oppressor!

The idea that a woman should learn male preferences and try to meet them if she wants a good man is a blasphemy these days.

Men also get the blame for young girls trying to improve their image by starving themselves on diets, wearing this, not wearing that, for having body image issues e.t.c., yet guys ruining their health with steroids, extending their legs in something that works like a medieval torture device is their own fault.

The redpill is hated because while it definitely sees women as human, it sees them as pretty self-serving and machiavellian humans, not the innocent little angels they are sometimes portrayed as. Also, while the spread of the redpill doesn't affect the alphas much, the betas become cranky and refuse to take a shitty deal, they try to play women back and dare to think they might deserve better. All of this makes dating more difficult for women.