That's the most positive take you can have on this.
Of course it won't catch 100% of it, but very few laws or measure do that (and those that do almost always come with very high amounts of false positives). Also links are not hard to scan for either, and you can't "just" upload CSAM to anywhere either and not expect troubles sooner or later (unless you know what you're doing, in which case we're back to the previous paragraph).
I think it's very hard to deny that of course it will catch a non-zero number of people, although it's hard to determine exactly how many beforehand. That doesn't mean it's a good law, it just means that all these type of "it won't even catch anyone!" argument are just bad arguments.
Sure, but it is still completely valid to argue that it won't quantitatively be effective enough to justify its cost, either in money or in creating-the-infrastructure-for-a-fucking-police-state. "Non-zero" isn't necessarily an acceptable level of effectiveness.
I don't think anyone really thinks that.
After a while the second, third and fourth won't be required.
Jeeze...we learned obfuscation fucking years ago (torrenting was punishable then, probably is still, and a few people may be made examples of, by ip tracking etc as subscribing becomes more disliked).
Outside public content can be scanned as part of "defense in depth" too.
They don't, or they don't care. Measures like these have two purposes:
1. To make it seem like someone is doing something. Constituents don't accept the idea that their representatives are powerless to fix certain hot-button issues. Even if a new law or regulation will have minimal or no effect on a problem, as long as legislators (or whomever) can pay some "experts" to say good things about it, many constituents -- most of whom don't understand the issues involved -- will be (somewhat) satisfied.
2. Continuing to establish and normalize surveillance technology and make it a part of normal life. The more that government types can mandate that people can't do in private, the easier it is for them to do... well... whatever they want to do.
If I'm sharing nasty stuff through one of these platforms and I can send text, I can send a link. In any platform "that doesn't allow links" you see people sharing them anyway through normal text, even if they have to create some new conventions. And you can also just use different platforms anyway, so where is the deterrent?
This is just annoying based on people legislating for technologies they don't understand.