Took ages on the below, and see the thread's run away with me - apologies to the new conversations I'm now interrupting and any subsequent posts addressing these points already, better than I do.
So...
Thanks. Interesting reply. The thing is, there are some things in it that I do think, again (with apologies for being somewhat direct) come from a rather superficial understanding of a hugely complex issue - and perhaps also activist talking points. I used to think the much same, but have read and seen so much since that I've now, regrettably, come to realise how much I was missing back then.
their lived experience and social reality probably has much more in common with women and girls
Potentially trans people are adding to and enriching the experience of what it is to be a woman
I'd question this from a number of perspectives.
Firstly, biology is relevant to our argument - if not as "fundamentally"(!) central as some activists would have us believe! Eg. Consider this WI group being set up to compensate for TW no longer being members, to discuss "experiences of what it is to be a woman", or suchlike. Honestly, the only times I actually think of myself as being a woman rather than, simply, a human or an individual, tend to relate to what distinguishes me from the male sex class: certain functions, discrimination against me on the basis of the type of body I have and women's historical oppression, my proportionate physical vulnerability etc. Please note, this isn't about "sex organs", but, instead, the practical realities of being female in a world designed for males, up to and including not having a hope in hell of getting Grade 8 piano because of male-default keyboards (still resentful) or being able to bloody reach the microwave in my own flat or office (crazy!), or feeling able to challenge the male taxi drivers who ask if I'm married or try to bully me into paying extra, knowing I'm too small to oppose them and will leave the cab conscious that they know where I live. I'm honestly not sure how transwomen's "lived experience and social reality" aligns with this. This isn't to (popular "gotcha") present myself as a victim, any more than than a Black person discussing their experience of racism would be. In fact, in a world in which racist verbal micro-aggression are utter anathema, it astonishes me that women have to make this pre-emptive defence when describing the challenges they face!
Secondly, I think it's really important to recognise that "transwomen" is a wide-ranging umbrella term. This was very difficult for me to accept at first, as it isn't the popular media narrative and is very difficult to discuss in this context especially, involving, as it does, some unpleasant reading and corners of the internet. It's summed up very well in another MN thread called something like, "Where do people think all the transvestites have gone?" This group, previously accepted unquestioningly as, at best, a humiliating imitation of what it means to be female, and at worst, a potential risk to women and girls, has been subsumed into the trans umbrella. For them, it's not about dysphoria, but sexual fetish - and there are clearly many of them. Their own accounts are particularly interesting to read (eg. Debbie Hayton), if sometimes somewhat sexually explicit (google Andrea Long Chu, who may or may not fall into this group, whose description of what "she" thinks it means to be a woman certainly corresponds to aspects of this, and see if you can stomach this - "enriching" for us it ain't!) Looking at such men's reams of photos is rather less advisable! I honestly find it hard to put into words how viscerally distressing I find the suggestion that the "lived experience and social reality" of a man who identifies as trans for this reason in any way reflects my own.
This then leads us to another, different group - the deeply dysphoric, like your son. Here, things are much more complex, and I've a huge amount of sympathy for such individuals, particularly today, in fact, as they find out that organisations that unlawfully welcomed them for years are now ejecting them. I know quite a few currently trans-identifying children (I phrase that carefully, given desistance rates) and it distresses me to think how their needs have been misrepresented and undermined by an unthinking ideology that, in its authoritarian bent, demanded the impossible and unreasonable of women and girls in their name, and has, ironically, thereby done them lasting damage. A more open, democratic approach (google eg. "the Dentons document") could have avoided or mitigated what your child is currently experiencing. But even then, I truly don't see what this group has in common with me. Logically - and evidentially - their main (only?) way to signify their internal trans identity is by adopting external behaviours and features stereotypically or commonly associated with girls and women (whether joining Guides, or wearing a dress, or undergoing hormonal or cosmetic changes). And I don't want women - me - to be associated with any external behaviours and features, or classified according to these! And I do want us to retain the option of single-sex groups, for the reasons I give above. There are also some males in this group who take this approach to such an extreme (google Dylan Mulvaney) that they make your concept that "trans people are adding to and enriching the experience of what it is to be a woman" downright offensive to me.
Then, there's the issue of transmen and non binary individuals. Statistics indicate fairly clearly, to my mind, that a good proportion of girls, particular autistic and lesbian girls, are embracing these identities as they see "woman" and "female" become crushingly associated with external, often sexualised, appearance - in part because of the the umbrella term "transwomen" and all it entails, and for a thousand and one other depressing reasons (including the proliferation of porn, which factors into all this in the most disturbing of ways - Jo Bartosch is good on this). I want "woman" to be, simply, a practical and necessary descriptor that is 99.9% accurate in capturing a demographic of humans with particular needs... and is otherwise utterly irrelevant to who they are - to what they wear, or how they behave, what they can do etc.
As long as transwomen continue to dilute who and what women are, and women's rights - and society's understanding of the most fundamental, essential aspects of this - in a way that I feel risks reducing women to something external and wholly unrelated to (indeed, that is damaging to) our demographic, I will continue to speak out in a way that some may mistakenly interpret as anti-trans... but that is, quite simply, pro-woman.
Basically, all I ask is that our identity is validated, too, as distinct and worthwhile, and that it's not forcibly subsumed into something so different, so complex and, sometimes, so very starkly in opposition to our needs. Think of these trigger-warnings the BBC is giving before hosting a speaker who may misgender a transwoman! In some parallel universe somewhere, where women are valued in their own right, another BBC is giving a trigger warning to women each time they call a male "she", "woman" or "female", in recognition of how utterly unethical it is to redefine a whole portion of humanity according to the internal self-perception of the portion that has oppressed them for millennia. I mean, marital rape (woman-as-secondary-to-or-extension-of-husband) was outlawed only a few decades ago in the UK! We're not a part of males, subject to and shaped by their minds and wills.
Or at any rate, we shouldn't be.