Look at it from the other side. The person who is getting mean comments tells someone at SO about it (maybe via a survey). Then the SO admins notice that in the surveys women are overrepresented in the population of "people who complain about hostility".
Perhaps minorities already get enough abuse and hostility every day on meatspace, so they are less tolerant of even minor hostility over the Internet. Since they have a limited amount of fucks to give, so to speak, they are more likely to leave the site for good after an unpleasant interaction.
Think of minorities as the canary in the coal mine. They are more sensitive, so they start leaving the moment the environment starts to become toxic. Left unchecked, the toxicity will grow and push away everyone else too, so you can't just ignore them for being "snowflakes" or whatever.
Our culture encourages women and minorities to speak up. White men are expected to endure abuse in silence.
Consider how much attention complaints from women and minorities receive, and how little attention (and how much hostility) complaints from white men receive (unless those men are individually powerful, of course). People tend to repeat actions that are effective, so women and minorities learn to speak up, white men learn to keep their complaints to themselves.
Edit: I'd like to thank those who downvoted this comment for providing a live demonstration of the phenomenon.
Right. So let's not do that. Instead of waiting for minorities to speak up, you should complain right away when an online environment turns toxic.
Since we were not aware until today that minorities received more hostility on SO, that means users really don't know other users' gender and ethnicity, so it's not like anyone will call you a sissy girl for speaking up.
We have been complaining about hostility on SO for years.
It's debatable whether women and minorities actually do receive more hostility on SO, they're more likely to speak up, or SO's management is simply more responsive to their complaints.
It's also debatable whether we are living in a simulation or we are actually brains in a jar, or maybe only you are real and I'm a conversational AI.
But it's pointless to debate things that don't and can't change what we choose to do. Notice that all three of your proposed hypothesis can't change the fact that SO isn't very welcoming and they want to change that.
I think I get it. They could have chosen to act faster, before being forced to act by the politics of inclusivity.
I personally don't mind though. In my city many positive quality of life changes were made only after some disabled people complained. I benefit from those changes too, so I don't mind the delay as long as it eventually gets done.
I agree, if someone (SO, your city, or anyone else) finally improves their community in a way that benefits everyone, that's a good thing.
And if, as is often the case, past complaints had little effect until a particularly favored interest group spoke up, it's also an opportunity to listen more effectively to people who may have been ignored.
Perhaps minorities already get enough abuse and hostility every day on meatspace, so they are less tolerant of even minor hostility over the Internet. Since they have a limited amount of fucks to give, so to speak, they are more likely to leave the site for good after an unpleasant interaction.
Think of minorities as the canary in the coal mine. They are more sensitive, so they start leaving the moment the environment starts to become toxic. Left unchecked, the toxicity will grow and push away everyone else too, so you can't just ignore them for being "snowflakes" or whatever.