I’m not seeing how this is related. Make a rule in the sidebar which tells the poster to post Musk content that community instead. And if he still posts, it can be auto-deleted/locked (not sure if this capability exists in Lemmy yet).

Edit: Also, the community won’t be on your feed if you block it. It can be a nice automod feature to automatically move posts to another community if it detects Musk/Twitter/X keyword in the title.