Genuine or not genuine, mass surveillance is a bad idea. Full stop.
There is no solution to the "problem" of some people sharing photos or other content which some other people don't like which would be compatible with either privacy or freedom of speech.
The issue to be solved here isn't CSAM, it's CSA. The CSAM is evidence; they should be using it to find and prosecute actual abusers, not trying to drive it further underground.