* The California state constitution granted a broader right than the US constitution, and the speech in question was required to be permitted under California, but not US, rules.

* The speech in question was admitted by both parties to not reflect upon the shopping center's views, nor was the speech disruptive to its activities. Thus, freedom of association isn't going to kick in.

That last part in particular is key. For social media platforms, it is DEFINITELY the case that the content they host is imputed onto their own views. Alternative sites like Parler or Gab are invariably referred to with a note that they host predominantly far-right content--these sites are known almost entirely by what they carry, not the principles the sites claim to espouse. Even for larger sites like YouTube or Facebook, the ability to find certain kinds of negative content on these sites periodically blows up into major media furors.

A more appropriate precedent is Miami Herald v Tornillo, which held that a Florida state law requiring newspapers to publish candidate replies to articles was unconstitutional.

Everything after the comma in that sentence is actually the entire point of why §230 was passed; prior case law held that YouTube would be liable for all content if it did the barest amount of moderation.