Section 230 and common carrier law is generally a legal shield for node operators in the US.  The uk courts have rejected the idea that node operators are financially responsible for node content. 

Criminal case law has always upheld that possession of illegal material has always required knowledge and control. As a node operator your node has no knowledge of what material is being transmitted  beyond that they are consensus valid transactions and you have no control over the valid transactions being included in the blocks. Deleting a bad block would exclude you from the network therefore you cannot control the network or the content on the network. 
The csam route is unsurprisingly the place they are going with this argument since csam is treated as a special case. However csam on the block chain is just a string of hex so trying to say a blob of hex data that is a jpeg is any different than fragmented  hex data that forms a jpeg is a huge stretch. Neither are csam or they both are. It doesn’t become csam until it is interpreted by software, weather that software is rare or common doesn’t matter since it is not part of the Bitcoin software it is irrelevant to the operation of the network.