There is no viable means of filtering out content. As long as transactions are valid they will hit the network because the network is made in such a way to make it hard to censor valid transactions. If one wanted to one could spend the fees to load extremely large files in several pieces on chain. You would have to fork bitcoin and remove a lot of the things that make layer 2s function to stop the easiest pathways and even then spam could still make it on chain.

The leading proponent and coder of knots was one of the og chain spammers having used the block header space on a block his pool mined to insert a biblical verse. He did this without the consent of the miners whose work was responsible for winning the block. This behavior cannot be stopped and that space is 100 bytes.

Bitcoin is not Bitcoin with kyc or gate keepers. It is permission less for a reason.