Of course we're not a significant minority.
Literally nobody outside of the internet crazyland, believes that if you're a woman, your genital organ might be a penis, unless they have serious reality issues.
Even the woke leftybros who pretend to believe it, look a bit sheepish if you ask them if they'd sleep with a "woman with a penis" if they're straight, or a "man with a vagina" if they're gay. Because they wouldn't, but they can't say so, because they'd have to admit they've been virtue-signalling in order to unleash their misogyny on women.
Everyone knows that men have penises and women have vaginas and that biological sex is real. This is not a minority view. This is what the majority believe and it is scientifically accurate, not hateful bigotry. And it does not imply that you accept gender roles or sexist stereotypes as inherent, if you know that biological sex is a real thing.
Pretending it's a minority view, is just a way of signalling to the rest of the media, that mumsnet isn't a heretic.