Transgender people have a mental perception disorder (they perceive a reality that does not exist). In the past, the answer has always been to try to guide/treat those afflicted with the mental disorder so that they can perceive reality correctly...not to make all of society encourage them to cultivate the disorder, and surely not to encourage children to cultivate a reality perception disorder.
Homosexuality is just a sexual preference, not a mental disorder. Gay men aren't having sex expecting to have babies, and we aren't requiring society to act like they could get pregnant at any time. All the parties recognize the biology that controls; no one is denying biological science; they are just saying, "Here's who I like to hug and achieve sexual release with." That is something that any adult can do without harming anyone, and without even harming themselves physically. They don't have to mutilate their genitalia to realize their full homosexuality; they don't have to partially but radically alter their biological body in an attempt to fully change their biological state.