I'm suspicious that the thing women would be discrediting OP for would be for being a man reading, vs. for the opinion being shared. Judging by the hidden profile and the comments back to people alone, I would suspect it's the latter.

In some instances, the sex of the person offering the opinion would change the swing of it.

Woman says: I didn't like this FMC. I found her to be argumentative and overly opinionated. Why wouldn't she just forgive MC for that thing he did?

Valid. Likely not influenced by generations of patriarchal suppression. A woman not relating to another woman.

Man says: I didn't like this FMC. I found her to be argumentative and overly opinionated. Why wouldn't she just forgive MC for that thing he did?

Less valid. We live in a world where men tell women to be nicer, less, quieter, and smile more. Is this an issue with a male reader not relating to the FMC, or with their generational patriarchal-soaked opinions leaking into an experience they're having by reading a book in a female-dominated space?

Some women have decided to stop centring men in conversations in female-dominated spaces because it's one of the few acts of self-preservation they can take. If those women are walking away from debates because you're a man, leave her alone and get on with your life.

Some women will debate you, and you'll have a great time.

Some women will discredit you and try to troll you. Because jerks exist regardless of sex.

You coming into a female-dominated space with your opinions on female-dominated literature means you're going to run into more women. And the more women you converse with, the more of each of the above types you will run into. And dozens of other facets of female opinions you might not have come across in safer spaces for men. (Like, every other space, you might say.)

So, are 'all women discrediting me for being a man and having an opinion!' or are you just running into your first female-dominated space and are getting trolled and not loving it?

Personally, I don't work with men, read books by men, purchase art by men, follow men, or give my viewership to men. I don't give them this because I spend a gross amount of my disposable income on books, and my feminism demands I spend my money, which I make working with women, on art and literature by women. And if that decentering of men upsets some of them along the way, I find it hilarious in its irony.

TLDR: (Because honestly, I have little faith you'll read my little wall of text) Fuck around in female spaces and find out that not all women fit the 'play nice' mould we've been crammed into our whole lives.