You didn't really give any legal perspective. Either Facebook owns the content and the liability as a publisher, or it's a platform and shouldn't fixing content towards what they want to show.
You're not making any sense. From a liability standpoint, there is no legal distinction between platform and a publisher.
You might be getting confused by the concept of a common carrier. Facebook is not a common carrier. It might be possible to amend the common carrier law to cover Facebook, but in the current political climate that seems unlikely.
Facebook is not a common carrier, but enjoys liability protections under the CDA Safe Harbor:
47USC230(c)(1)
"(1)Treatment of publisher or speaker
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."
And definitions--
47 USC 230(f)(3)
The term “information content provider” means any person or entity that is responsible, in whole or in part, for the creation or development of information provided through the Internet or any other interactive computer service.
Of course, CDA also excuses Facebook from making tilted or faulty moderation decisions in good faith.
You are mixing up two legal concepts: one is intellectual property ownership; the other is liability for republishing what others say. They are two different bodies of law: IP law (copyright/trademark) and tort law (libel etc.). They are analyzed under separate legal lenses.
