Miners won't get in trouble for mining a block with CSAM. It's not as if the miners are standing around their rigs masturbating to the blockchain. Even if they WOULD get in trouble, choosing not to mine a particular block wouldn't help, since just by virtue of the fact that they recieve transaction requests means that they will be downloading arbitrary transactions, even if they choose not to add them to their blocks in the end.

The only people who can be hurt by this are the little guys.