Under section 230, Fox News is not liable to suit if someone not affiliated with Fox posts illegal content on their comments on their website.
They are liable to suit if Fox News employees post illegal content on their website.
Twitter has the exact same treatment under the law today. It’s not liable for suit when Trump tweets lies about Joe Scarborough. But if @jack or @TwitterSafety tweeted the same lies, it could be sued in court for libel and section 230 would not be a defense.
Fox and twitter are already equal in eyes of the law today.
Fox News is already publisher under any reasonable definition.