CSAM is, by definition, photography or videography of something that has already happened. Therefore, quite literally, doing absolutely nothing about CSAM itself would result in no harm to any child, as the harm has already occurred.

Now you're probably going to then cry about incentivising or normalising CSAM - but that's a different argument. And if you then try to argue that the normalisation of CSAM would somehow encourage people to abuse children, well then you're really off into the zero-evidence weeds. Go look at porn research (the actual Google Scholar/JSTOR/Elsevier kind), and you'll see that almost everybody who looks at porn neither wants to nor would actually do what they see in porn, if they were given the opportunity. Surprise, surprise, most people wouldn't actually get gangbanged/bukkake'd/fucked by their sibling, mom, dad, grandpa/pooped on by their next door bespectacled red-headed neighbour, etc.

Nor is there any evidence that inadvertently coming across CSAM turns people into pedophiles (news flash: pedos were turned on by kids long before they were ever exposed to CSAM on the internet), and porn itself is almost invariably used for fantasy or as something wholly unrealistic that people get off to precisely because it's unrealistic. Even though it might be unsavoury to do so, we could follow this reasoning to its extreme but undoubtedly true conclusion and state that there are individuals who get off to CSAM notwithstanding that they would never themselves abuse children.

So to recap, 0 children would be saved from harm because the CSAM itself is ex post facto; it wouldn't de-incentivise CSAM because the demand and markets for CSAM and pedophilia existed long before the internet was a thing, and pedophiles will find avenues around dumbass implementations like Apple's scanning (TOR, anyone? not using an iPhone/Mac?); and, finally, just because somebody looks at CSAM doesn't mean they're an actual pedo or would ever harm children themselves. The fact that possession of such material is illegal is not to the point - Apple is not the police, and the police and other executive agencies need warrants for this kind of thing (in common law countries this notion is more than 400 years old).

Meanwhile, we know the false positive risks are not insignificant - look at the white papers yourself, or just look at the numbers that smart people have crunched. The best part is that even though Apple says the false positive rate is 1 in a trillion accounts, people's photo libraries are exactly the sort of thing you can't extrapolate statistically. Maybe your Aunt June really likes photos of her nephews in the pool, and she's got a library with 300 photos of her nephews half naked and swimming when they visited her last year. Apple has no fucking clue whether they would or would not trigger its scanner, because it currently does not have access to Aunt June's unique photos to test vs its database. Apple quite literally doesn't know what the fuck will happen. I and many others find that abhorrent when you consider the effect that even the mere accusation of pedophilia has on a person's life. And that isn't even to start the discussion of what kind of precedent on-device scanning would set for other subjects (political and religious dissent, for example - if not in America then in places like China).

Apple and everybody else can fuck right off with this Orwellian shit.