No. If they go through being trans, and regret it later, it's going going to fuck up their whole life. Let them grow up to think for themselves first
there's plenty of other things they can do to "fuck up their whole life" that our country seemingly doesn't mind, this one doesn't seem that different.
driving a car and living on your parent's back in a rented out apartment is nowhere near the same as swapping your gender and neither of the two examples results in manipulating your body's biological structure and mental state of mind
i didn't mean a direct comparison between the act of driving and this, more so that our laws consider people to be an adult on a very gray scale. traffic accident? you're an adult you should know better. trying to smoke a cigarette? you're not an adult can't do it. ok you're 21, legally able to drink alcohol, great, you're an adult now; still can't test drive a car, you're not an adult.
now disregarding the specifics of the examples, I did say
if they have heard the words of a medical professional and have received counsel but still decide to proceed, that should be their decision. I'm not saying let some 15-year-old pop into CVS or Walmart pharmacy and immediately pick up some hormones or whatever.
If they do end up regretting it, then it's a valuable life lesson that they can then work towards fixing with other medical procedures.
To put it rudely, let them fuck up their life if they want to, why care so deeply about what someone else wants to do? If they're being forced or pressured to do it, yeah stop that, but yet again, if they have been screened by a doctor and possibly a psychiatrist or something of that nature and they confirm they know what they're doing, let them run wild.