I can't stand Trump, think he's already the worst President in our history, but I have no problems with this decision. I'm an army brat, I was in ROTC, went to basic, had all the training to be a military officer (just never signed up), and I know 1st hand and personally of people being either kicked out or prohibited from joining for all kinds of medical issues, some of them ancient history, some of their mildly debilitation. The idea that someone is going to physically alter their body in extremely intrusive fashion that requires all kinds of lifetime medical and even surgical regimens to maintain them and the military is supposed to 1.) pay for it 2.) make concessions for the other commitments to that surgery; is a real head scratcher.
My only problem is Trump obviously did it as another one of his twitter shiny bauble, public debate distractions.