I'm really conflicted about this. For context, I deeply hate the abuse of children and I've worked on a contract before that landed 12 human traffickers in custody that were smuggling sex slaves across boarders. I didn't need to know details about the victims in question, but it's understood that they're often teenagers or children. So my initial reaction when reading this Twitter thread was "let's get these bastards…
The NCMEC database that Apple is likely using to match hashes, contains countless non-CSAM pictures that are entirely legal not only in the U.S. but globally. This should be reason enough for you to not support the idea. From day 1, it's matching legal images and phoning home about them. Increasing the scope of scanning is barely a slippery slope, they're already beyond the stated scope of the database.
My point is that we have no way to verify the database wouldn't be abused or mistaken and a lot of that rests on the fact that CSAM is not something people want to have to encounter, ever.