I think that being blind is as isolating as being deaf, but in different ways.
Whilst it is clearly going to be harder for a deaf person to learn to read, it is perfectly possible most of the time, so they shouldn't be restricted to BSL as their only form of communication.
I think I can explain the divide.
Deaf people who never had the option of cochlear implants learned to live their life to the fullest and some created a community of BSL users. Within that community, they are not disabled. Deafness is normal and everyone is on an equal footing. They feel that their deafness is an intrinsic part of their being and they don't feel 'broken'. They have accepted themselves for who they are and do not want to be fixed.
They don't want to have to fix themselves in order to be accepted within the wider hearing community and if the wider community think that they need to be fixed, then they reject the wider community.
Then some of them take the decision that they do want to be able to hear and they take the 'cure' of a cochlear implant. Someone doing that is seen to reject this deaf community, implying that everyone remaining within it is broken.
Even worse is when a parent has a deaf child. The 'Deaf' community says that the parent should love and embrace their child for who they are and not try to 'fix' them because they are not broken. If they 'fix' them with a cochlear implant, then they have rejected them for not being perfect, so they will offer no support to them.
So you end up with a divide between those who have accepted and embraced deafness, and those who have been deemed to reject it, despite the fact that it is perfectly possible to accept the deafness but still seek a cure.
It's the cure/don't cure divide. I have seen similar divides in other disabilities, but none quite as severe as in deafness. Autism can be pretty bad but it's not quite as clear cut.
I hope that makes some sense!