Anyone who seriously believes that sex can be anything other than male or female - or who seriously believes that you can change sex must by definition be confused / delusional / have mental health issues - or be living a lie with some ulterior motive...
you state that Being trans is a real axis of human diversity with a durable biological underpinning. Other than 'real axis of human diversity' having no substantive meaning - there is no biological underpinning to the concept of being trans. There isn't a single person anywhere in the whole world, in the whole of history who has ever changed from being a man to being a woman - or vice versa. However much surgery, however many chemicals, however they dress / look / speak / etc. they will still be a man.
If all that 'trans' meant was a set of people who bumbled along confused and unhappy with their sex, then you might argue that they are just different and that is okay - but as a compassionate society we should look after such people and give them the ability to come to terms with their natal sex and biology.
However over the last few decades it has increasingly meant more than that - it has meant men - the dominant sex gaining access to places they should not be - it has meant bullying of women and the vulnerable, it has meant lies and deceit, oppression and violence, it has distorted society and taken us to a place we should never be where 51% of our population are under threat of eradication of identity by a small subset of men with ulterior motives - so no, different in this instance is not okay - lies and deceit are not okay, violence and oppression are not okay.
It cannot be changed through therapies - wrong, it is a mental health condition - and there has been clear evidence that e.g. for those who are pre-pubertal and who have been lead to believe that somehow their mental place and health is a result of being 'born in the wrong body' - for a very high % of them, going through puberty reverses much of what they felt as they come to terms with their correct sex and body. - The leading of children into hormones and body butchery will be seen as one of the biggest child abuse scandals of our era.
there is nothing inherently wrong with it whatsoever Actually there is - there is never anything right about living lives based on lies - the deceit that says you can change sex or gender leads people into operations and chemical treatments which wreck their bodies - by pushing a damaging agenda the 'trans movement' has harmed many people and stopped them from taking the route they might otherwise have chosen - to treat the mental health issues etc.
With the right support/ healthcare trans people can live perfectly healthy and full lives without mental health challenges. Correct - but that support is treatment of the mental health challenges, it is not to lie to them and society, it is not to pretend that something can happen that is impossible, it is not to oppress women to validate a lie, it is not to abuse children...