This is one of the things I help families with, with children. Empower them along the lines of something like this:
“I love you and nothing you have told me changes that. I appreciate your distress and I want to help you. Equally, I am still your parent and you are still my child and we need some boundaries. We will remember that you cannot actually change sex. This is imperative. I will consider calling you by your new chosen name, but you need to understand the difficulty that brings when I have an emotional attachment to the name I chose for you 12-15 years ago and 12-15 years of calling you that. I will not be compelled by you, nor your Internet friends to use the wrong sex pronouns for you. Not only is that something I can’t change about you, it’s also something I have been doing for the last 40 years of my own life. You don’t get to control this because, as a child, you don’t get control over the language of adults around you. We are setting out now that just because we disagree on things, it doesn’t mean I ‘want you dead’ or am not your ‘real family’ or any of that nonsense. I will not compromise my beliefs on women’s rights because of our family situation either.
“You should understand that, knowing my beliefs on this issue, that I believe therapy and avoidance of undertaking irreversible medical changes is something I feel strongly about. I will support you with that. I will support you full stop. But I will not let you undertake anything I think you may regret later in life. You are still a child and I am your parent. As well as loving you I have responsibility for you, something people on the internet you might chat to don’t. If I express concern or opposition, it’s because I love you.”
And I get them to ban the internet
.
Funnily enough, with this I find parents are happy, feel like they can be supportive without telling lies, and importantly, the children feel happy because despite what Stonewall et al tell everyone, children appreciate support and boundaries.