Just to satisfy people’s curiosity on OP_RETURN.

When you start a new node it must download and validate all blocks/transactions starting from genesis to construct the UTXO set― a database of all unspent outputs needed to validate future transactions.

Technically since OP_RETURN outputs are not spendable they do not go into the UTXO set (though they do remain in the blockchain). Also once you download and validate the UTXO set you can theoretically delete the historical blockchain as you no longer need it to validate transactions going forward.

So theoretically if there was child porn in the chain you could delete it from your node.

However, if every node deleted the cp, from the chain then you couldn’t bootstrap new nodes as they need the historical chain to build their copy of the UTXO set.

So SOMEONE needs to store the cp and serve it to people. If everyone deletes it then the system doesn’t work.