Bitcoin is defined by users and the node software they run that decides on what transactions get into the next block along with verifying those transactions and deciding if that block is valid and which chain of blocks is valid, and then storing the full blockchain on their node (there are pruned nodes which are less useful).
Currently, a few of the Bitcoin Core developers are captured and advocating that in the next version of Bitcoin Core (v30) they’ll raise the value of OP_RETURN to 100,000 bytes, which was previously set to 83 bytes in Bitcoin Core and 43 bytes in Bitcoin Knots (often just referred to 80 and 40 bytes). This is extra arbitrary data not having anything to do with the financial transaction, which has been used for hashes to verify documents or other data off the Bitcoin block chain or on a sidechain. And the Bitcoin Core devs have no logical arguments for this change to add this much extra data which will take up disk space on nodes, slow down and limit transactions per block, raise transaction fees, incentivize others to flood the chain with data to profit from…
Since node runners are in the way of taking over Bitcoin, a theory is that with this much extra data, child porn could be included in the blockchain to put regular people running Bitcoin nodes in a precarious position. This isn’t without historical precedent, as child porn has been found in the Bitcoin Blockchain before, but obfuscated requiring quite a bit of effort to retrieve, and granting plausible deniability to node runners. But with blowing up OP_RETURN data limits, it could be added without needing to be obfuscated to where a Bitcoin node runner could be in criminal jeopardy. Which could drive node running to major Bitcoin corporations who can take advanced measures to filter this content possibly with legal protections, while running your own Bitcoin node ends up with you having child porn on a computer within your home, business, or rented hosting facility. And without regular users running nodes, the promise of Bitcoin will be lost and who would stop even worse changes to the protocol by these captured developers and those backing them? Could it be to damage Bitcoin and drive everything to stablecoins or captured Ethereum?
A longer presentation by the Bitcoin Mechanic being more philosophical along the way.