Children choose their sex?

First of all, the youngest reassignment surgery in the world was at 16.
Second, a person can't just choose to change their sex and go and get surgery the next day. There are many psychological evaluations, and a person has to live as that sex for 2 years in the USA before they can get surgery.
Puberty blockers aren't generally used and a person can't take puberty blockers until they have reached puberty. Hormone therapies in almost all cases are not allowed until the person wanting to transition are 16.
The age for surgery in the US is 18. In Canada, top surgery can be done at 16.

Dressing for the gender one prefers is not the same as having surgery. Identifying as one's preferred gender is not the same as surgery.

Now as I recall from our conversation about Prince Andrew, you had no issues with 17 year olds being able to prostitute themselves, so why would you have an issue about them making other decisions about their body?

In Canada you can.https://nationalpost.com/news/canada/canada-transgender-treatment

i would say we should be very careful on this topic, cuz, like all things in life, it's extremely complicated.

and it's extremely sensitive and touchy as an area of course.

as laid out in that article, there have been cases of gender dysphoria identified for a long time. until the very recent past they were rare, they were mostly in males, the behaviors were seen at a very young age (pre-teens) and generally those males 'grew out of it' and many of them became gay men. some did transition and live their lives as women, and if that's what they needed, then great. that shoudl be supported.

but the fact that we are seeing cases more in teen girls, and in particular in teen girls who to that point in their life often hadn't shown any kind of gender confusion, suggests we're looking at something very different here.

some are callng it a social contagion. that seems like a slightly antagonistic way of saying it, but it may be getting at a truth of what's happening here.

i'm not sure that we're doing teen girls, who suddenly declare themselves to be trans with no apparent history of that, any favours by supporting them in that belief. in at least some of these cases, we may be looking at adolescents having a particularly tough puberty, getting unwanted sexual attention as often happens for teen girls, & seeing this possibility promoted through social media as an outlet, a potential escape.

some have made a comparison to anorexia, and that's another comparison that might be contentious but it might be very appropriate in some cases.

There are doctors who support hormone therapy for children under 16, so it's not unimaginable.

Personally, I don't support these kinds of surgeries (or most plastic surgery) until the body has stopped developing. Puberty is a confusing time for each and every one of us.