Holding broadcasters accountable is easier than holding "narrowcasters" like Facebook accountable because you don't see what narrowcasters are promoting. But when you do find out you see that it is things that broadcasters would never push both for ethical and commercial reasons. This is important to consider.
But primarily commercial reasons related to having a completely different distribution model.
Even if you held that coverage of Russia's role in the 2016 election was promotion of a conspiracy theory it would still be an obvious false equivalence to compare that to the promotion of groups like Bugaloo (that has killed multiple federal officers) or QAnon (which has resulted in multiple kidnappings, many other crimes, and promotes the worst antisemetic conspiracies invented, and more far more absurd things).