Galaxy
This one doesnt, but it isnt unreasonable to try to exclude a demographic. Tricky but not unreasonable.
I would think any woman who went on a site which acted as support group for men to speak about their mental health was an absolutely horrendous human being. I would think any man who went on a site for women survivors of assault was also a tool. Many sites by their nature are exclusive. Hard to police obviously but they can be aimed at specific groups.
A site can be aimed at a group (eg for supporters of Wolverhampton Wanderers) or can be moderated to exclude discussion of anything other than recipes using peanut butter, but it is all but impossible to ensure than only certain people can access it. I post on boards where you have to be a member for 6 months and also have 100 posts before you can access private areas. This means that regulars can use the private forums to discuss personal matters in relative safety, but even then, human nature is such that we all know there could be breaches, in the same way that telling a trusted person a secret is risky in 'real life'. It's good in that it prevents things like invasions from Reddit or wherever to bully posters who have different opinions, though, and people can get advice about a difficult boss or relative without fear of them seeing the thread.
I don't understand why someone would want to intrude on others' privacy, or post somewhere they aren't wanted, although I realise that it happens. They must have strange lives if that's what they feel a need to do, but the Internet is a strange place.