Postmodernism has been very useful for feminism. The theory is that some ideas which were called 'natural', 'obvious', or 'biological' might actually just be dominant discourses (this is Foucault). For example, it used to be said that women are naturally nurturing, and so should stay at home with the children. This was thought to be rooted in biology. Heck, we still have to fight the idea that being potential childbearers makes us less reliable workers. So the postmodern approach has allowed us to deconstruct these ideas and to say they are ptriarchal constructions.
The trouble is, we can't choose what to deconstruct- it's an all or nothing thing. This can end up feeling really nihilistic, so when the very idea of 'woman' is deconstructed, it shakes our foundations.
Judith Butler (don't freak out) notes the value of strategic categorisation (eg as a woman) but warns against what or who we risk excluding. I can't unthink this, or reject it. Through history there are loads of examples of the construction of who's a human (or a man, or a woman, or a Muslim, or a Jew, or a priest) and who isn't. It's so dangerous- dehumanizing can lead to horrible results. Just look at the GC bedfellows. David Davies! Sarah Vine! I'd be concerned.
I know my point of view annoys or upsets many here but I'm not trying to do that- I really do want to hear people's responses. The appallingly rude, bullying responses of some from behind their keyboards does nothing to help the conversation. I've been told I'm not a woman or a lesbian, and that I must be influenced by a man. This in itself is an example of dehumanization.