Tech companies, primarily Facebook, Twitter, and Alphabet, get nearly blanket immunity from responsibility for the content that’s published on their outlets. Section 230 of the Communications Decency Act, which was instrumental to their initial success, gives them that broad immunity, based on those companies’ initial status as agnostic pipelines that merely provided a place for disparate commentary to be promulgated.
Protected monopolies (vis., pre-breakup Ma Bell) gave government-sanctioned special, protective, treatment to selected companies in order to facilitate their initial success. There came a time when that protection no longer was warranted, and the protection was eliminated.