Section 230 is about who's liable if speech either breaks the law or causes damages in some way unprotected by the First Amendment. That's the table-stakes of the discussion. It's a little silly to bring up the First Amendment given that context.
230 is about who is NOT liable. Platforms are NOT liable for what they don't moderate, just because they moderated other things. It protects them from imperfect moderation being used to claim endorsement.
