Speaking of mutilation and religion, are we ready to stop mutilating male infants and children — AKA circumcision ?
Let them decide as adults if and when to do this irreversible mutilating procedure!
It's not really life changing, and can arguably be done as an agent in the best interest of the child, even without any consent from the child or indication that they'd be interested. It can be assumed that it's extremely likely that as adults, they will not be unhappy with the procedure having been done, and that the results will not be a significant material impediment to their future lives and the path they decide to follow. This is why people don't like comparing circumcision to FGM (which is debatably a much more apt comparison).
If the child wouldn't indicate that they are interest in undergoing the gender affirming surgery, is there anyone that would say that the parents have the right to forcibly have it done to the child (the way they do have that right when it comes to most medical procedures)? If a parent would do this, would it be sanctioned, or would criminal charges be brought? Is the only difference here that the child has expressed interest and displayed tendencies which make one think that this is an appropriate move?
(The logical response to this would be that a parent that amputates a healthy child's foot would be locked away, but one that does do to a child with gangrene in an effort to save their life would be supported and praised. It is obvious that circumstances do inform course of action. At the end of the day, it does come down to one's belief in the necessity of said action being taken in fiduciary interest of the custodial charge, and the likelihood that this is the action which the child will appreciate in adulthood. I do recognize this.)