Banning it for minors isn't fundamentally different than banning untested medication. If you don't like the government making medical decisions, well, this is a fringe part of that issue.
Treatment for precocious puberty isn't equivalent to treatment for gender dysphoria. This is another topic that has been dealt with at length already in this thread. I will just note that the entire point of using blockers for precocious puberty is that the effects aren't reversible. Stop taking the drugs, and you don't get precious puberty. That's a permanent effect, and it's both desired and beneficial. Halt regular puberty for any significant length of time (which is the norm for these treatments), and it will not resume as normal. Miss the window, and it's gone for good. And there are serious negative consequences of that.