Call me niave, but what is wrong with conversion therapy in theory?

I get the historic roots of it being linked with anti-gay/LGBT activities and it being problematic about 'fixing' what essentially are healthy sexual functioning (e.g. it's fine to be gay).

But it's not black and white and surely 'some' gay/bi men and women suffer distress and would prefer to be straight.

And likewise for 'trans' children and adults - perhaps there are effective ways to reduce/eliminate gender dysphoria. Do such methods really always have to seem bad.

Note: I am neutral on this / have many gay friends. It's purely from a theoretical perspective.