No worries, and it's a good question.

First, at least according to The Guardian iirc, there's already CSAM on chain, and forking it at a blockheight in the future won't remove that. So if the argument is that anyone storing this data on their computer will be liable in a court of law, then that ship has already sailed or the chain needs to be rolled back to ~2017.

Second, embedding CSAM on-chain was already possible before the op-return increase, which was reasoned to be included to disincentivize other forms of data storage that are more harmful to the network, such as by bloating the UTXO set.

Third and most importantly, this proposed legal theory simply does not hold up in the face of anyone familiar with the law. Bitcoin nodes (and bitoin miners) are at least by US regulators largely understood to be facilitating communication, and communication providers are not liable for the content they relay or host.

Interestingly, holding communications providers liable for the content they host was a large part of the original cryptowars. If that theory had pertained, the internet would simply not exist as nobody would be willing to build services with such a risk attached, as Google, Facebook, Microsoft, Amazon, etc would routinely lose Billions to hosting CSAM.

Hope that helps.