I support men and women however they identify (because I am a human being and treat others as I expect to be treated) but if their inner feelings led to self harm I wouldn't affirm, in the same way I wouldn't agree with an anorexic man, woman or child, they were fat. I would want someone to do the same for me.
I wouldn't affirm a child in their identity that they were a superhero who could fly if they were on the roof preparing to jump off but I would encourage a child to use develop their imagination whilst instilling a sense of reality so they don't grow up completely miserable that every wish isn't granted, or seriously injured from a fall or deeply depressed aged 21 that the Tooth Fairy doesn't actually exist after all.
The OP said this was not a discussion but it was posted on the chat thread. Perhaps it would be better in Feminist Support? Just an observation.
Though it's clear many posters agree with the OP. Maybe the OP wanted the support for trans women to come in the form of agreement that biological sex can be changed? I don't know, the OP is long gone and I'm late to this.
Discussion around self ID on boards across Mumsnet has only highlighted and taught me about safeguarding and why we have it, and also why it's everyone's responsibility. It has also taught me about laws, why we have them, what we base them on and why we should consider the motives of those wishing to change the law (this goes for a whole lot of law reform before anyone jumps).
I have also learned a lot about sexual fetishes and 'kink shaming' and how that ties in with safeguarding and children protection, for all kinds of reasons, one being Pride that is embedded in the LGBT movement (though it began as a civil rights movement for same sex marriage and anti-discrimination law and acceptance in society) it is now a commercialised parade of 'equality', roundly rejected by many gay men and lesbian women.
If self ID supporters and proponents of the transgender ideology hadn't made demands of #NoDebate and insisted that everyone bow and repeat their mantras, that we had to sign up to one way of thinking and if not we are labelled as old fashioned, outdated, transphobic bigots who don't understand 'science' and are comparable to Nazis, I don't know, maybe we wouldn't be so divided now and maybe the backlash the LGB communities and women are facing wouldn't be so terrifying.
I think if the OP only wants responses that agree with their view then I would say Mumsnet probably isn't the right place for them as you get a plurality of views and MNHQ provide this platform with a free speech approach.
It's a shame the OP hasn't come back to engage further.