Have you considered the problem of doctors, married parents and other legitimate people being labelled as CSAM users and pedophiles? This has already happened, and they are not obligated to take the brunt of misjudgement of tools developed to judge such media. This is not a hypothetical scenario, and has already happened in real world, and has caused real world damage to people.
The argument of planted CSAM is not incoherent, but has also played out with many people. It is one of the favourite tools for elites and ruling politicians to use. I am less worried about it because such a law thankfully does not exist, that will misjudge the masses brutally for fictional media.
If a pedophile creates a hospital/clinic room setting and photographs a naked kid, will it be okay? Do you understand these problems impossible to solve just like that? Parents also take photos of their kids, and they do not take photos like a doctor would. They take photos in more casual settings than a clinic. Would parents be considered pedophiles? According to the way you propose to judge, yes.
You are basically implying that social defamation is what matters here, and the trauma caused to victim of such fictional media is a problem. However, this is exactly what anti-AI people like me were trying to warn against. And since these models are open source and in public hands, the cat is out of the bag. Stable diffusion models work on potato computers and take atmost 2-5 minutes to generate per photo, and 4chan has entire guides for uncensored models. This problem will be 100x worse in a couple years, and 1000x worse in the next 5 years. And infinitely worse in a decade. Nothing can be done about it. This is what AI revolution is. Future generations of kids are fucked thanks to AI.
The best thing one can do is protect their privacy, and photos from being out there. Nobody can win this battle, and even in the most dystopian hellhole with maximum surveillance, there will be gaps.