However, if sites like Facebook, Twitter, YouTube, etc. go beyond just preventing illegal content then they are behaving as publishers and should be suable for any content or subsequent actions resulting from that content.
This is not a simple question of "private companies should be able to do as they please" or "the 1st Amendment doesn't apply to private companies".
That’s right, and it’s Section 230 that assures that. It says lame-ass bloggers can’t sue Jim just because they think Laz defamed them.