Rainboq said:
To respond to what you just said: A child can often feel ashamed of varying from percieved societal sexual normals, hence why coming out of the closet is a huge thing, IME.
It's not so much about sexal norms as it is about the idea that sexual identity is so important to them that they feel the need to have corrective surgery. I would feel just as appalled by the thought that my child wanted penis enhancement medication or breast augmentation; well, probably more so, given the extent, expense and potential risk of the procedure of sexual reassignment.
I would see this sort of thing as a very strong deviation from the guiding principles I would lay out as a parent. You want to be homosexual, that's fine. You want to have a more group-oriented sexual lifestyle, I'll warn you about STDs, but otherwise give you the freedom to live that way if you want. But the second you start thinking of sex in terms of such self-definitional terms as that invoked in transsexualism (also including spending too much time watching pornography, dressing deliberatively provocatively for the sake of unqualified sexual attraction, or working in prostitution in later life), I will step in to intervene.