What if you had a baby and discovered it had a neurological condition that meant the only language it would ever be able to learn was Mandarin Chinese? If you lived in China or already knew that language it wouldn't be much of a problem. But if you lived in the US, Canada, or western Europe and didn't know that language what would you do?
Would you forbid your child to use it, hoping the diagnosis was wrong? Or would you do everything possible to learn Mandarin yourself and find situations where your little one could interact with others who use that language?
If you were a smart and loving parent of course you would choose the second option.
Not too long ago that's the sort of choice parents had to make when they learned their children were couldn't hear. For a long time the philosophy was that forbidding deaf children to use Sign Language would motivate them to learn to speak and read lips.
A hundred years ago when lots of kids lost their hearing due to infections and diseases after they had already been hearing and perhaps using spoken language that approach might have worked for some of them. But by the mid twentieth century medical advances had made it very rare for people to loose their hearing for those reasons.
Instead, most deaf children were born that way because of prenatal damage and forbidding them to learn Sign Language meant they would have no exposure to language at all. Of course some deafness is hereditary, but kids from Deaf families would learn to sign from their parents.
When I started working at California School for the Deaf in the 1960s I was one of the first people who knew American Sign Language who was allowed to work with the young children. At first the kids who were not from Deaf families had tantrums all the time, but as soon as they learned to sign the tantrums stopped.