it would be nice to have a forum with solely other parents, which one can assume was the point, as everything is aimed at parents on the site
Well then you are simply wrong to make that assumption. The “articles” on the home page are aimed at parents but the talk boards are the real heart of Mumsnet and there are vast areas of those that are NOT aimed solely at parents (and some, like the infertility boards, deliberately aimed at non-parents). Nobody thinks “ooh, I do love the Mumsnet Eastenders discussion threads because I only want to know what parents thought about last night’s episode” or “I must go on the cat lovers’ threads to see what some parents think about cats today”.
The site evolved like this- parents came on to discuss parent stuff like which was the best pram to buy. As they were also people with interests beyond their children, the chat naturally strayed into non-parenting issues. Whole topics grow up around those and non-parents joined in those discussions. While on the site, those non-parents might then also have joined in some of the parenting chat, perhaps sharing experience from their own childhood (even most non-parents have been parented after all...), or about their relatives, or their professional experience with children, or just generally contributing a point of view.
And in any event it is simply impossible to impose any criteria whatsoever on people who contribute to an internet message board, which is why you have talk guidelines instead. Like in any discussion you are free to choose how much value to attribute to a certain person’s opinion based on what you know about them, but you have to exercise that judgment, not scream in to the wind for people to get off “your” forum. There could be any number of people on here making up active lies about being parents and purporting to give you experience-based advice and you would never ever know that they were not genuine; at least if someone is honest about not being a parent you can then choose to skip past their comments if you don’t deem them valid.
You are about 10 years too late if you want to interact only with parents on this site.
And the reason that all this kicked off was not because you expressed a wish for a parents-only forum, it was because of the staggeringly rude way in which that point was made. And repeated ad-nauseam.
Oh and your suggestion above that any childless person chooses that status and can change it is downright offensive to those with infertility issues. I hope you’re proud of yourself.