tl;dr – The First Amendment and Section 230: Protecting free speech on the internet
The First Amendment and Section 230 immunity work together to protect free speech on the Internet. Attempts at Section 230 reform based on how online platforms use their editorial discretion will run into Constitutional limitations.
But… online platforms have a First Amendment right to adopt whatever content standards they choose. With very few exceptions the government may not mandate speech. But a law requiring online platforms to adopt a particular set of content moderation practices — say, to maintain a “balance” of political views — would do just that. Conditioning Section 230 immunity on online platforms giving up their right to editorial discretion would be unlikely to survive the strict standard of review to which such government regulation of speech would be subjected by the courts.