Scanning publicly accessible material makes a lot of sense and is within the boundaries of section 230, tech companies are responsible for policing removing illegal or threatening material. For private or encrypted information, section 230 does not apply.
The purposes these services were designed for matters. iCloud is meant to be private, facebook would prefer everything you post is public as it’s built in to benefit their business model. Facebook should scan, iCloud shouldn’t. You are purposely obfuscating that detail.
Apple is introducing a reverse 'Little Snitch' where instead of the app warning you what apps are doing on the network, the OS is scanning your photos. Introducing a 5th columnist into a device that you've bought and paid for is a huge philosophical jump from Apple's previous stances on privacy, where they'd gone as far as fighting the Feds about trying to break into terrorist's iPhones.
"Well you can turn it off" to "Well, but then you just don't trust Apple".
Clearly these are users who did trust Apple. Apple betrayed their trust. Given that Apple bulk handed over iCloud data to China, I don't really believe their pinky promise that they are, by policy only, going to resist government use of this tech. They can cave to government cases _and_ the government can certainly force them to.
Therefore you must trust Apple. So if you still have issues then you don’t trust Apple.
Trust is fragile and Apple has taken what in the past I believed it understood to be a strategic advantage and stomped it into little pieces.
Not only has it been possible for a decade, it’s been happening for a decade. Every major social media company already scans for and reports child pornography to the feds. Facebook submits millions of reports per year.