I'm so sorry to hear what's happened Polyplax. All of us on this thread completely understand how you are feeling right now 
Knowledge is absolutely key for us ROGD parents.
When a child suddenly 'comes out' as trans, it's like being hit by a juggernaut.
We're 2.5 years down the line and are only now connecting with other parents. We were so caught up in the shock, manipulation, gaslighting and associated behaviours that go along with this that we retreated into ourselves in order to process everything and survive.
The battle is always centred around truth and reality. And that makes it extremely hard when each individual young person is absolute that this is how they feel, have always felt, will always feel. That's an almost impossible premise
to challenge and terminates further thought and discussion.
Trying to maintain a neutral stance, based on facts, actual past history, correct information and concern for your child's health and future is the most loving thing we, as parents, can do.
Of course, young people caught up in this will not thank us for that approach, as they are told everywhere they look that they must be fully accepted as their 'authentic self' or else. The 'or else' means that for many of us
with older independent children, we have been estranged. The message is that they should cut off from family and friends who don't collude.
If our children are given time, unconditional love and acceptance for who they actually are - without affirming their trans status and identity - then we can hopefully help them to keep their future options open.
When we did finally connect with other parents we saw how similar every story is. Everything our child insisted was about her as an individual, actually belonged to a collective narrative. Our child has done everything possible to shut down critical thinking amongst family and friends - divide and rule, for or 'against'. It's heartbreaking - but it's all part of it.
I'm starting to see that the only way forward is to join our stories and knowledge together, keep hold of the truth, and to do everything we can to insist that clinicians provide an alternative to the affirmation pathway, via therapy and other psychological services.