Anyone serious about making a platform that operated in this matter would recognize the need to implement a means for pruning the blockchain when content of that type was flagged as illegal as a core feature.Blockchains are forever, so anything blockchain-based will have that issue. That's ultimately a problem for the maintainers of blockchains.
For instance, there is arguably CP and other illegal content in the Bitcoin blockchain itself, so theoretically anyone who maintains a full node with the entire chain is duplicating that.
Generally a focus on the legality of a technology when it is known to be used for illegal conduct is whether it also has substantial legitimate uses. However, the intention of the technology's creator is part of the context in which this is judged, and CP is an issue where authorities have been known to be remarkably harsh in evaluating such conduct.
Of course, for Pedowheels associates, that wouldn't be a feature. It'd be a bug.