The child would not get the kind of benefit from the CI that he got because he was implanted young. The research clearly shows that the longer the brain is without auditory stimulation the harder it is to learn to interpret the sound. By waiting you are clearly choosing to make the benefit less or at the very least much harder.
The parents could have chosen to continue to sign and include the child in the Deaf community. They didn't have to stop. Plus, I have never heard that becoming a part of the Deaf community is "long and hard".
And you didn't say that the child was language deprived, but that he had social issues, two totally different things.
