When I close the browser tab with neoreaction, I have a decent chance of never meeting a neoreactionary in my real life, so the problem is solved. Unfortunately, I cannot say the same thing about Tumblr!feminists. They are also rare, but I have already had the "pleasure" of meeting three of them. (Twice, they have cost me a female friend, because they were a friend of the friend, and have successfully convinced my friend that I am an evil person, because I happen to have an Y chromosome, which is a huge red flag for them. The third time, they have publicly accused my friend of being racist, when she dared to say that some traits correlate with certain genes, in a group of people who previously said more or less that genetics is a burgeoise pseudoscience.)

Unlike neoreaction, feminism happens to be a topic in real life (one could even call it a billion dollar industry, if we include all the government money spent on gender studies, female-only projects, etc.), so its perversions have a real impact. Many people spend a lot of time online, and if they meet the Tumblr version first, some of them will conclude this is the true version.

What country do you live in that allows you to think these things only exist on the internet?

so I have no idea where such a forum would be hosted

It may strike you as anarchy, but pretty much anyone can host a forum on the internet for insignificant amounts of money or even for free.

Imagine how intolerable NRx would be if it were to acquire one of these.

Of course we have one, but it's secret.