Access fairness has absolutely nothing to do with protection, and even within those laws, and the FCC only governs purchased spectrum. It does not, for instance, cover cable operators and its ability to regulate the internet is severely limited.
Cable operators are governed by equal opportunity rules for political candidates. Politicians extending this to social media will probably be the next step.
I can find no law, or regulation, which specifies that cable operators are governed by those types of rules. Broadcast media (radio and television) are. As far as I know, Cable operators who run political ads do so because of the money they generate.
But the carrier can apply rules for the ads, and as long as they apply uniformly those rules are fine.
The problem is that “conservatives” have made their platform be one that denies basic human rights to protected classes and the platforms have banned such speech from both ends of the spectrum. If you want your speech or ads to violate the platform rules you are saying that not only does the government get to say “you must carry our message” but also it gets to dictate the rules of those messages