Women talking together without appropriate male supervision has always been terrifying to a certain demographic. Women who have given birth are frightening and unpredictable, as are, oddly, women who haven’t given birth and so placed themselves outside of the “norm”.
Women banding together and talking always works up a good head of castration anxiety among men who are that way inclined 
Therefore Mumsnet, being an unapologetically female centred space where men cannot exercise control must be written off as irrelevant and silly.
Trouble is, when you exert yourself to do that, you’re showing your hand - things that are irrelevant and silly don’t need to be so energetically dismissed, do they? Because, well, they’re irrelevant. You don’t need to enthusiastically try to disempower something that is already powerless.
It really is very helpful when the blatant sexism is exposed like this:
Mummies: stupid, easily led, easily frightened
Stay at home mummies: lots of time on their hands to sponge off their husbands and get worked up about things
Mumsnet: ought to be focused on how to feed babies, choose a pram and nothing else
Moral imperative: re-educate the mummies into better thinking