>"No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider." This federal law preempts any state laws to the contrary: "[n]o cause of action may be brought and no liability may be imposed under any State or local law that is inconsistent with this section."
> No provider or user of an interactive computer service shall be held liable on account of — any action voluntarily taken in __good faith__ to restrict access to or availability of material that the provider or user considers to be obscene, lewd, lascivious, filthy, excessively violent, harassing, or otherwise objectionable, whether or not such material is constitutionally protected
...and that specific requirement has been specifically referenced in Trump's recent executive order.
'gnopgnip may be referring to the much broader liability shield, for the content that you do not remove, which is provided by (c)(1) and has no good-faith requirement. That is Twitter's main "legal protection from defamation and libel" that you mention above.
Trump's executive order suggests that the (c)(1) liability shield could go away if you don't meet the (c)(2) good-faith requirements, which I gather is not considered a strong legal position.