Tech has to be built for someone. You build for people you (probably) assume have eyes and ears and hands and written language and a financial system and a predictable reward mechanism and a notion of privacy and on and on and on. The only thing that makes a product "good" or "bad" is its interaction with a massive stack of assumptions you're making about the user.

But you only know like 0.000002% of the possible users of your product. So really you're extrapolating wildly from a tiny set of clues about your user, based on signals sent to you by your culture. (Where "culture" is just the set of stuff that filters through to you about the people around you who you don't know personally.) And that culture holds some people to be more "normal" than others. Consider (as just some examples) that test subjects start to see a crowd as half women when it's much less than half. A movie poster with women on it is intended only for women; a poster with men on it is for everyone. A movie poster with only black people is intended only for black people; a poster with white people is for everyone ...

So the product you build is based on a dirty signal -- it incorporates a massive stack of assumptions about the user, derived from a culture that you know is lying to you about what a normal person is. If you build for your internal idea of a "normal" user, letting tech be tech, then you reinforce whatever happened to be handed to you without realizing you're doing it. That's why this is a conservative ideology.

"Feminism" in this context is a progressive tool -- it's a way to look at your product with fresh eyes. How do anonymity tools look if we assume that all users are equally important, focusing on the experience of men vs. women? Huh, it seems that the user base includes a significant number of men who are hateful toward women, and that has a big impact on who participates in anonymous forums and how men and women experience them. Now we have a lot of different options for dealing with that (censorship being only one, and obviously not one the Tor project would choose). Before we* used this lens, our only option was to ignore it and preserve the status quo.

Other "-isms" are just other tools. Anything that your culture cares too much or too little about -- and therefore tends to lie to you about -- is a possible lens to learn about users you're ignoring, because your mental model of "normal" doesn't match reality.

(* Note I'm not at all affiliated with Tor, just using "we" generally here.)