OP
Our concern for children transitioning probably feels, to you, unsupportive. It's often called "hate" and "transphobic".
We would call it concern born of experience.
There have always been trans people; a tiny number, whose lives were genuinely made better and happier by transitioning.
Since 2010 something different has been happening. There has been such a huge explosion of teens identifying as trans. Over 4000 percent increase in those who take it far enough to get referred to the Tavistock. This disproportionately affects natal girls (XX) who as children had not expressed repeatedly and insistently that they were uncomfortable in their gender.
Those of us who are now adults, parents, we worry about this. We don't hate you, we don't deny your existence. We worry that this may be at least in part a different form of teen subculture like punks, goths, emos etc except that with this one, you do stuff to yourself that will potentially affect you for the rest of your life.
You might say the spike in transmen as teens is simply because we're more broad-minded, it's less of a taboo and more socially acceptable. But that doesn't stack up. Because if it were just more acceptable to present as the man you always felt like now - where are the late transitioning women? Where are the women in their 30s, 40s and 50s who are now finally able to become their "true selves" and become transmen? If it's just that our generation was oppressed from living that way, why aren't we transitioning now? It's because the vast majority of us no longer feel dysphoric. We may be lesbians, we may be gender presentation non conforming women, we are all sorts of people - but we don't feel like we have to "become" men.
We don't hate any of you. We want our teen kids to be happy, we want you to be ok. We want you to live fulfilling lives. We want you to be mentally and physically healthy. We accept that there were always, through history, a small number of people who need to live as if they are the opposite sex to find peace. We don't see that every teen who comes out as trans is correct that this is the only pathway for them, because we know that brains do change and mature. We wouldn't mind, though, if it was just a name and clothing change, a social transition, nothing permanent. But it scares us when our children start to take hormones and remove body parts that will potentially make them sterile and medically dependent throughout their life, when the stats suggest and looking at society suggests that many of them are not making the only choice to bring themselves long term peace of mind.
We don't hate our kids. We love you.