That statement is not based on statistics. It's based on my opinion which comes from what I understand the objectives of CS are and what I have read and heard from those that have used it.
As far as isolation, I am talking about isolation from communicating with the majority. The non-signing hearing population. If you can only sign and are not literate then you have isolated yourself from communicating with the non-signing hearing population. If you want to communicate with non-signing hearing people (the vast majority of the pouplation) then you either need to be able to speak and speechread, or you need to have enough literacy to read and write. How else would you communicate with them? And if you can't communicate with them, that, to me is isolating yourself from them.
