Its funny but I've brought those same things up and all I get is the transphobe label thrown at me for it.
First of all, I have never once been given a good reason to encourage kids transitioning genders. Doing all of that stuff to a child before puberty seems like it would do a lot of medical harm to the child. Also, I don't know if you've ever talked to a child, but they have wild imaginations and just say shit that comes to mind, and their likes and dislikes can change without prompting, but its also easy to coerce them and get them to say whatever you want them to say. And teenagers will do anything for attention or rebellion, and that in forms a lot of their bad decisions too. The people least capable of making the informed decision for gender transition are young kids and minors. If my kid ever said they wanted to transition, my immediate response would be "Come back to me when you're an adult and paying your own bills, then we'll talk".
Remember that episode of King of the Hill where Bobby got into that Christian rock group that tried to present Christianity as "cool" and "rocking"? Not only did it give us one of my favorite Hank Hill quotes ("Don't you see, you aren't making Christianity better. You're just making Rock and Roll worse") but also one of his best lessons. At the end, he showed Bobby pictures of him in Ninja Turtles costumes, and his old digital pet that he hasn't played with in years, basically demonstrating that fads come and go and Hank wrapped it up by saying "I don't want The Lord to wind up in this box". Well, replace "The Lord" with "your genitals" and that's pretty much how I feel about kids transitioning. The major difference is that, yes, fads and hobbies come and go and you can just throw that stuff in a trash bin with no permanent harm done...but you can't get your penis back.
And the whole perverts in the bathroom thing, this is where I really got hit hard with the transphobe rant. "Oh, so you think all trans people are perverts?!". And my response was "No I don't, but do I think that a pervert would take advantage of this, call himself trans to get access to a women's bathroom, and then rape a woman? Yeah, I do". They just want to implement this across the board and not expect us to ask any questions or bring up these concerns, which is really a confusing message after living through the whole #MeToo thing.
Again, these are reasonable concerns and questions that should be answered, but people like us and JK just get called names and told to shut up.