Taking that as unvarnished truth [0], for the sake of argument, that's not at all an ambiguity, it's a crystal clear status.
> Yet, even though they have many of the legal protections of being a pseudo common carrier, they have none of the obligations, such as the obligation to treat all content equally.
Again, taking that as true for the sake of argument, its not an ambiguity, but a crystal clear status.
Its a conflict with the false dichotomy of the idea that the only two roles in information dissemination are fully-liable non-neutral publisher and fully-immunized neutral common carrier. That model isn't true offline, and it's not true online.
[0] Which it isn't, because while the CDA and DMCA (and others) provide some limited/conditional protection, they are not a total bar to liability; but the still the status is not ambiguous, merely distinct.
Yet, even though they have many of the legal protections of being a pseudo common carrier, they have none of the obligations, such as the obligation to treat all content equally.
For example, it is illegal for your phone provider to eaves drop on your conversations and censor your phone conversations.
But it is NOT illegal for facebook to do the same thing. Why are they treated differently?