Thank you, /u/sarahpratt. Calling someone "pussy whipped" is a lot like saying "you left because you wanted to sin." They're both ways of dismissing a person's reasons for leaving The Tribe (whether that tribe is The Church or The Bro Club). When someone chooses to leave the tribe (especially if they seem happy about it!), it implies that there's something wrong with the tribe--why else would anyone leave? Rather than face the possibility that their tribe is dumb, the remaining members resort to lowering the value of the one who leaves.

"You just wanted to sin" is what anxious church members say when they need to diminish the legitimacy of someone's reason for leaving the church. "He's pussy whipped" is what bros say to one another when they need to diminish the legitimacy of one of their former members' choosing a relationship with a human woman over continued allegiance to The Bro Club.

"You just wanted to sin" has bite because even while it acknowledges the attractiveness of leaving the church, it casts the person who remains in the fold as more virtuous than the one who leaves. It suggests that the one who leaves is a sad shell of their former self. "Pussy whipped" has bite because even while it acknowledges the desirability of having sexual access to a woman, it casts the Bros who remain dismissive of a woman's full humanity as holding higher status than the "whipped" guy, who treats his wife's/gf's interests as if they matter. The implication of calling someone "pussy whipped" is that she's not a person deserving of respect; she's just using the promise of sex (or the threat of no sex) to get her way, and in the process, she's making a once-dominant man into something to be ashamed of. "Pussy whipped" is premised on the idea that men ought to dominate "their" women. It goes along with the belief that someone who doesn't dominate his woman doesn't deserve to be called a man. Men control women, or they're not real men.

On the whole, Reddit tends to be a hostile place to women because it's so infested with thinking like this, and this subreddit is no exception. That's why we don't hear as many first-person stories of women who leave the church while their husbands remain. It's pretty obvious that showing off your Bro Club credentials is welcome here, while being female--or speaking of women as fully human--is less so.

All that said, not every situation that gets a guy labeled "pussy whipped" is just a case of his treating her like a full human whose interests are worth prioritizing. Some women do indeed dominate men, and when it happens, it's important to take it seriously. It happens less frequently than the reverse, because our culture tends to tolerate it less than we tolerate men dominating women (and because men tend to be socialized to find dominant women unattractive, while women are often taught to make themselves submissive or else no one will like them), but it does happen. Thankfully, it's possible to talk about that problem without dismissing her humanity just because she's a woman, or by shaming him for failing to fulfill his assigned gender role by controlling her. The way to do that is by labeling it "abuse" or by calling her "abusive." I invite you all to try it.