Wait: DSM-V concludes that transgender identity is a psychiatric disorder? I must have missed that part......
The DSM-5 does not state that transgender identity is a psychiatric disorder, nor did the DSMIV, nor did the DSMIII-R. The requirement for gender dysphoria to be present as a condition of diagnosis for gender identity disorder was introduced to DSMIII-R way back in 1987.
Throughout these thread incarnations you have made a series of statements about the DSM that are demonstrably false. These include that the DSM-5 'declassified' gender dysphoria as a disorder (it is a disorder in DSM-5), that DSM-5 declassified transgender identity per se as a disorder (it was already not a disorder, see above), that legislation passed by governments is based on the 'new understanding' of transgender identity in the DSM-5 (although the diagnosis hardly changed at all, only the name), and even that reforms such as the GRA are based on this new understanding despite the fact that the Act was passed nearly 10 years before DSM-5 was published. You have repeated some of this nonsense multiple times despite it being corrected.
At one point you even implied that the reason sex reassignment surgery is allowed, whereas amputating a limb in somebody with BIID is not, is that transgender identity is recognised as 'valid' whereas BIID is not. This is despite the fact that you also imply it is only recognised as 'valid' since DSM-5, published in 2013, while sex reassignment surgery has been available for decades.
You have also persisted with 'appeals to authority' based on the DSM-5 while also implying that your understanding exceeds that of Dr. Zucker, the leader of the working group who revised and wrote the current chapter on gender dysphoria and the world's foremost authority on gender dysphoria. For example, Zucker has strongly criticised spurious parallels between the concepts of gender identity and sexual orientation, has opposed gender identity being included in conversion therapy bans for that reason, has stated that government policies on gender affirmation ignore relevant science and are driven by activism, and believes that the rise in adolescents identifying as transgender is likely due to social contagion, amongst other things. However, when experts disagree with you, the experts are apparently wrong.
(And how do you reconcile the fact that progressive governments all over the western world, acting predominantly on medical advice and wider consultations,
You have not produced a shred of evidence that governments are 'acting predominantly on medical advice' and copious evidence has been provided that they are not, which you have ignored. Therefore your assertions can be dismissed.
are giving transgender people substantial rights and protections in law?
Transgender people have already had 'substantial rights and protections in law' for some time. For example, the Gender Recognition Act' was passed in 2004 in order to allow people who had transitioned to marry a partner of the same birth sex, 10 years before same-sex marriage was legalised. Gender reassignment has also been a protected characteristic since the 2010 Equality Act and does not require any medical transition or gatekeeping.
What is being pushed by activists is not 'rights and protections' but an ideological position of sex denialism that seeks to replace sex with gender identity in law and policy.
Don't you think that if the medical community - at national and pan-national levels, were saying something like "actually, it's our view that people with transgender identity are suffering from a mental health disorder, and they need treatment rather than this degree of accommodation and rights-giving", the policies currently being enacted would be.... rather different?)
Straw-man, see above.