I think 9 years old is way too early for this, and the psychiatrist who diagnosed the child should be more skeptical. As with any medical condition and treatment, there is such a thing as too much, and as doctors, psychiatrists should be making decisions that minimize harm to the child.

If the child, of their own volition, not coerced by their parents were deciding for this to be done, then puberty blockers seem like a good step until they are well within their teenage years and can take hormones. But it seems somewhat clear that the parents are pushing this idea on their child, and just as a trans person suffers from Gender Dysphoria, so will a cisgendered person who has wrongly undergone transition. You might say, so what, they can always go back? Well it isn't that easy. There are negative social, neurological, and physiological effects of transition. 

I am confident the doctors can figure this out without the state directing them in the long term, but the casualties until we get there are alarming, but if we don't get there casualties will exist (for trans people) also.