Think about this: everybody would be doing this if you could get away with this. Illegal content stored on secret Internet sites with complicated access protocols (port knocking) and multiple layers of encryption is still illegal.
Plausible deniability. If you really think illegal content stored in the blockchain is an issue for the network, you should check
freenet.
There
is illegal content on freenet. After all, it is primarily designed to store content, unlike Bitcoin's blockchain.
Like the blockchain though, this content cannot be removed. It's decentralized, redundant, encrypted
Live with it.