I'm fine with child (prepubescent) rapists whom are adults to be sentenced to death. If you were an accomplice to that, as a videographer or similar, I'm also OK with death.
(There's a really weird social area from 13-18, with the weirdness and illegality going away up at 18. Stuff in this realm, especially around 2 similar ages, gets very stupid. This is where you can get 2 16yo's sexting and being charged with CSAM of their own body. I'm avoiding this in this post.)
But what does this CSAM scanner do? It only catches already-produced pictures of CSAM. In other words, it's evidence of said crime. In no other area of criminal law is there a law against said evidence itself. And yes, given the statutory nature of these images (possession is criminal, even if you didnt' put them there), I'm not at all comfortable in charging people for simple possession.
Even if they have urges of liking age-inappropriate pornography and "CSAM", as long as they're not doing any physical actions of harming humans, I'd much rather them do so in their own bedroom alone.
Nor do I buy into the gateway theory that CSAM leads to production of CSAM by raping children. This smacks to me of the DARE drug propaganda and gateway theory (which is complete bullshit).
And, we also already have harder situations that have been deemed legal: SCOTUS stated that Japanese Manga Hentai featuring schoolgirls (obviously under 18, sometimes by quite a lot), are completely and 100% legal. Again, SCOTUS foscused on 1fa and the fact that no children were harmed in its production.
And that leads to what just happened a few days ago. With the Zelenskyy (badly done) deepfake, when can we expect 18yr women with very petite bodies, being deepfaked into 10-13 year olds? In those cases, we could attest that everyone in the production is of legal age and provided ongoing consent. Will this fall under the same as Hentai?
Tl;Dr: I'm for the criminal legalization of CSAM. I'm for death penalty for child rapists/child sexual assault. But this, I can see going very very bad, in easily overscoping CSAM to the "cause of the day".