The main issue is that the system is basically a bit of snitching spyware dolled up with cryptographic magic to make it only work with really bad stuff, honest.
As recently posted on HN [1] one should be very wary of backdoors, no matter how much one believes only the right guys could ever use them. Once they're there, they're there: it's arrogant beyond believe to think that opponents of yours won't exploit them.
I won't use an apple product with this feature. I've been using apple's ecosystem since about 1994.
I understand your points on backdoors, but I don't understand people trying to argue that the "Cryptographic Magic" is the bad part that will send people to prison due immediately upon "HASH COLLISIONS", in my view, takes away from the actual concerning points.
What most people are focused on is that this is spyware built in to the operating system. The fact that perceptual hashes have some weak points could also lead to problems, but that's not the main focus of most opposition to this system.
As recently posted on HN [1] one should be very wary of backdoors, no matter how much one believes only the right guys could ever use them. Once they're there, they're there: it's arrogant beyond believe to think that opponents of yours won't exploit them.
I won't use an apple product with this feature. I've been using apple's ecosystem since about 1994.
[1] https://twitter.com/matthew_d_green/status/14334701097425182... and https://news.ycombinator.com/item?id=28404219