Before then we had control of most media by a small set of companies (with many fun documented examples of people being blacklisted for going against the owners). Before that we had the Television Code, Comic Code, and so on. Before that we had McCarthyism.
Public and media speech was always moderated. In the past it was simply harder to notice since there were fewer un-moderated channels.
The FCC is an unelected, mostly unaccountable entity. I think George Carlin had some things to say about them. That they have any control over transmission of anything outside of a technical, practical scope is a travesty, imo.
Beyond the hardened strawmen of actual written law, we have a shifting sense of what is publicly acceptable. Given that most people do what everyone else around them is doing, or at least what they believe others are doing, there exists a powerful tool in that to control the public discourse. We've gone from "I disagree with what you say, but I will die to protect your ability to say it," to "I think someone will find this offensive, so I will also find this offensive, despite my not knowing anyone who'd actually be offended by it."
The laws are a harder target, so those who would wish to stifle inconvenient discourse likely would find it easier to convince a mostly pliable, trusting public to not say the things they don't want said. That there still are a small number of companies controlling what a majority of people consume might be convenient to this.
All conjecture, of course. More of the Paul Harvey "If I Were The Devil" kind of thing.
Public and media speech was always moderated. In the past it was simply harder to notice since there were fewer un-moderated channels.