Abuse by who? It's themselves who are against adopting it. It's just autonomy at work.

Parents and children ?

Sure Adults opting out of such treatments on such grounds is fine. Parents doing so to their children, not so much.

I mean you can't exactly go, "We'll wait for them to be old enough to make the decision for themselves" for hearing.

Abuse of deaf children. Being able to cure deafness in a child and not doing so isn't much worse than intentionally making the child deaf.