Apple's trouble with CSAM is from its approach to new features

Apple's method, its motus operandi, is to design a product or process and present it to its customers. There is no discussion (at least none outside of Apple), there is no gathering of opinion, there is no debate. Apple decides, implements, and sells. Apple dictates, customers follow.

We can see this behavior in Apple's hardware.

Apple removed the floppy disk from the Macintosh. Apple removed the CD drive from the iMac. Apple removed the audio port on the iPhone.

We can also see this behavior in Apple's software.

Apple designs the UIs for iOS and iPadOS and has very definite ideas about how things ought to be.

This method has served Apple well. Apple designs products, and customers buy them.

Yet this method failed with CSAM.

Apparently, some customers don't like being dictated to.

One aspect of the CSAM change is that it is a change to an existing service. If Apple changes the design of the iPhone (removing the audio port, for example), customers still have their old audio-port-equipped iPhone. They can choose to replace that iPhone with a later model -- or not.

If Apple had introduced a new file storage service, and made CSAM scanning part of that service, customers could choose to use that new service -- or not.

But Apple made a change to an existing service (scanning photos in iCloud), and existing iPhones (if Apple scans the photos on the phone). That presents a different calculation to customers. Instead of choosing to use a new service or not, customers must now choose to stop using a service, or continue to use the modified service. Changing from one cloud storage service to another is a larger task. (And possibly not possible with iPhones and iPads.)

Customers don't have the option of "buying in" to the new service. The changes for CSAM are not something that one can put off for a few months. One cannot look at the experience of other customers and then decide to participate.

No, this change is Apple flexing its muscles, altering the deal that was already established. ("Pray that I do not alter it further," quipped Darth Vader in a movie from a long time ago.)

I think that the negative reaction to Apple's CSAM strategy is not so much the scanning of photos, but the altering of the existing service. I think that people now realize that Apple can, and will, alter services. Without the consent, or even the advice, of the customers. I think that is what is bothering people.