How do you ever have a social media network that is immune to this from now? You could with the best intentions start a non-profit, defederated, open-source, grass roots social network. It would go great, until the moment it hits critical mass and becomes prey for people who are willing to piss in the pond to make money.

There's no way to defend against it. You can just copy and paste text from an LLM into the reply box.