I would argue that this Apple system is not so much surveillance as a censorship mechanism. They check for a finite set of "bad" things that no one is allowed

I would argue that this Apple system is not so much surveillance as a censorship mechanism. They check for a finite set of "bad" things that no one is allowed to have. Because they went so far out of their way to avoid learning anything else about your photos, I think the argument is going to get very messy if we try to argue the surveillance angle. It gets very nuanced very quickly, and public opinion doesn't do nuance well. It's a censorship tool. This argument is straightforward and easy. China can add Tank Man to the list of bad hashes, and now nobody is allowed to see him. The entire argument is now about what information should be censored, and who do we trust to maintain the badlist. (Edit: Otherwise I agree with everything that matthewdgreen wrote above.)