Let’s pretend for a moment that this is true.
No matter how much that some on the right might portray it as cruel experimentation á la Josef Mengele, a better comparison would be ECT (Electro-Convulsive Therapy, AKA “Shock Treatment”). While largely forgotten today, during my childhood it had a bad reputation, with all the associated horror stories. The truth is that when it saw common use, it was over-prescribed and occasionally inappropriately prescribed. Sometimes it was done incorrectly, especially early on before research got a handle on how to do it properly, resulting in permanent damage and/or trauma. It also didn’t help its reputation that, in the US at least, electrocution was a common form of execution. This still saw use not because doctors were evil bastards (okay, a few isolated cases…) but because sometimes, it worked. Today the things which ECT was used to treat have other, better treatments, but because not everything works the same for everyone, it still exists as a backup option, and is safer than it used to be. Even if this was an ECT-like situation, it’s still the best possible option which currently exists, and the occasional detransitioner horror story isn’t a good enough reason not to make use of it, because it’s also irresponsible to just leave people to suffer and maybe die just because the treatment isn’t ideal.
Of course, this is all pretending that this turns out to be true in some unknown future time. What if it’s not? What if the better treatment isn’t available for centuries, how does it help anyone alive today?