Naturalistic Fallacy... There is no order in nature, there is only the constant but futile struggle to maintain that balance between order and chaos. In a few billion years, the Earth's "homeostasis" will fail and the runaway greenhouse effect will occur, turning Earth into Venus. But nature doesn't care, it continues trying to find that sweet spot between order and chaos. Humans are a by-product of that, and we have done many terrible things to unknowingly destabilise the balancing act. But transexuality? That evaporates in comparison to what we have done to this planet.
Sorry, I would have get out, but I am going to but in, and say this completely undermines the scientific method and process of scientific method, which assumes and relies on such fact that there is order (within reason of course). Secondly, your statement that it is constant, then loses also its basis. Thirdly, I think futility is a poor excuse to justify anything as excusable, I am not fatalistic, and certainly not nihilistic.
"But nature doesn't care, it continues trying to find that sweet spot between order and chaos." - Prove that statement, it is very ambiguous.
Sorry but your comparison to "what we have done to this planet" is much also a faulty comparison fallacy, as you yourself imply, so your argument makes no sense at all. Your argument is because the world is going to waste anyway (via greenhouse), then we should allow anything that does not add to that, does not justify transgenderism as normal.
This world certainly has other issues to deal with, but two things to note, children are already as early in kindergarten, been told confusing messages from education about gender and sexuality and
it is not helping the transparency on this issue. (The education system is acting like same-sex marriage is already legalised in Australia).
Secondly, why call it a "gender identity disorder" if it is perfectfully natural. There are things called CAIS (cannot remember the other one), that lead to other gender disorders and including
intersex people.
Is it ethical to give the right to a kid to decide whether they wish to transition. No, I think it is unwise, particularly if it is, which it can be, something else, or only a temporary phase (which it sometimes but not always is).
I agree more with Flop21, we don't get kids to make other big life decisions (I am talking about under 13 year olds, teenagers might be a different story), and this falls under that.