Censorship is needed to some extend. Block KNOWN spammers transactions from RPC. They can run their own nodes if they want to.

Needless to elaborate further. Known spammers are annoying. It is not because the blockchain is censorship resistant that everyone running a node or an API must accept transactions transmitted by known spammers.

Juts implemented a blacklist. If the transaction is a post or comment by a spammer ignore/reject it.

Spammers will still have their freedom of speech, by running their node they can keep spamming, that is unstoppable. For the greater good thought public APIs should make spammers lives more difficult