This letter assumes Apple is too stupid or has overlooked the risks of the tool they've built. I guarantee this isn't the case.
We have to assume given the pressure Apple has been under to build a surveillance tool like this that any "abuse cases" such as identifying outlawed LGBTQ content is in fact exactly what this tool was built for.
Apple have already proven their willingness to bend the knee to the CCP with actions such as App Store removals. I almost can't blame Apple for this because in all likelihood if Apple refuses to cooperate they will eventually lose market access. Couple this with the fact today Apple is seeing increasing pressure from western governments to surveil and censor "hate speech" and "misinformation" they've probably reluctantly accepted that sooner or later they will have no choice but to spy on their users.
What I'm trying to say is that Apple isn't the problem here. My guess is Apple's engineers are smart enough to know this technology can and likely will be abused. They're also probably not that interested in spying on their customers as a private company in the business of convincing people to buy their communication devices. Apple did this because governments have been demanding this. And in recent years these demands have not only been coming from the CCP and other authoritarian regimes, but also from governments in their primary markets in the West.
The only way we can fight this is by demanding our politicians respect our right to privacy and fight for technologies like e2e encryption on all of our devices.
I don't want to be overly negative, but realistically this isn't going to happen. Most people who use Apple's devices don't understand encryption or the risks content scanning technology present. And even if they did, no one is going to vote for a representative because of their stance on encryption technology. It seems almost inevitable that the luxury of private communication for all will eventually be a thing of the past.
I'm just glad I know how to secure my own devices.