All we're accomplishing with patronizing a boy or girl and allowing them to pretend they're something else is destroying a young life.
It's sick and it's evil.
Allllllllll of the reliable evidence supports the OPPOSITE conclusion, that allowing trans people to live the way they personally identify has FAR better health and well-being outcomes than the opposite. There's no other method of treatment for trans people that has comparable outcomes.
You can believe that it's mental illness or that there really are people who are "born in the wrong body." Either way, the medical evidence has demonstrated quite clearly that the most effective way to treat them -- i.e. help to prevent suicide, substance abuse, etc -- is to respect their chosen gender identity and provide treatment accordingly.
I think the problem comes from the fact that, while most are willing to provide respect to trans individuals (not because they want to engage in their "treatment", but just out of decency), some of those same people don't necessarily want to be told that they are wrong for seeing it as a mental illness.
There should be room for people to view it as a mental illness and still treat trans people with respect. Also, those who view it as a mental illness should respect those who don't see it as a mental illness and vice versa. As long as trans people are being treated with respect, reasonable disagreements should be tolerated on both sides.
It is a difficult thing for many in the trans community because their acceptance in society is so closely tied to their identity. It is exactly that that they are searching for. They have a sense of their own personal identity, but it's very important to them to know their place within the existing structure of society since it is so conventionally structured without a designation for them. This is why many trans activists speak of issues as matters of existential importance. This is why many feel threatened when not tolerated or simply accepted. It is crucial to them to be, not only trans, but accepted as trans.
Nevertheless, trans people (as all people) would be benefited by, as much as possible, living without regard to how society ascribes their belonging to it, and the conventional/traditional world should focus on common decency and respect for all people who don't fall in line with existing structure.
But because of the difficulty in achieving this ideal, we have reactionary movements to compensate for perceived inequalities, when inequality is the very nature of individual identity. For so many people, their identity is both personal and social, which I suspect at certain levels, is unhealthy, and perhaps could be labeled as a mental health issue. You can know yourself, but you can't force others to know you, or know only a certain part of you. You don't fully control how others see you. To not accept this reality, could lead to maddening anxiety, frustration, alienation, violence, self-harm, regardless of sex, gender, orientation, race, age, socioeconomic status etc.
There are a lot of unhealthy mental states in the world and many of them are commonly accepted. I'm not sure its always better that they are, but I'm confident that when dealing with them, it is better to do so with respect.