A kid shouldn't be able to a make decision that will impact their whole lives in a whim, because they aren't developed enough to understand long term repercussions. A kid doesn't just wake up one day and say that they're a woman inside, that idea was put into his head by someone else.
This fad will blow over eventually, and people will look back and see it at best as a the fetish that got out of hand, and at worse as we see lobotomies today.