I don't know enough about it to have a strong opinion of it being a mental illness, but from what I have read, it does feel that way. Of course, they would come back and argue how their brains are different, that a "trans" "female" who's biologically male has a brain that resembles a female's, so that justifies their choices - yet some of them would use the same argument to demonize us. It's OK to have a brain that's different, but only if it's approved by liberals.
Parents of trans kids seem to always be extremely defensive - like "it wasn't us, we didn't did do anything, it was all him/her" - to me, it raises questions. Though, I feel that a lot of kids - society has now made gender this fluid, bullshit thing. If you're a man/boy, and want to be a woman/girl, you can just snap your fingers and that's what you are now, and vice versa. Children and adults are not only permitted, but encouraged to question their gender. And now it's gone past permission, tolerance, and encouragement, to reward. And I think kids who are given not only this much latitude but are encouraged to question their gender and then led by society to "become" the opposite gender do so even if they were maybe just curious about it, or perhaps out of really nothing at all.