The Fairness Doctrine was a way for the US federal government to control the airwaves and ensure that not too much information from the so-called Remnant was disseminated in the post-World War II sociopolitical and economic environment.
The Remnant was actually a rump group of free-market thinkers, writers and philosophers that made common cause to oppose World War II during the 1930s. The Remnant represented the Jeffersonian agrarian republican "rump" that had been vitiated by post-Civil War statism but still existed nonetheless, especially in the post-bellum South.
After World War II, America was a much different society than before the war. Veterans returning home for the most part wanted little or nothing to do with political activism or freedom-related issues. Rightly or wrongly, World War II veterans wanted to reap the rewards of the tremendously powerful society that America had become.
After World War II, there was no more powerful society on earth than the combined Anglo-American cross-ocean state. With the fairly enthusiastic cooperation of World War II vets, America especially plunged into an evolving form of corporatism that gave rise to a rigid and hierarchical culture that ironically mimicked in some of its aspects the very fascist political systems they'd fought so hard to overthrow.
It was into this environment – one complicated by the Cold War with the USSR – that the Fairness Doctrine was introduced. It required that those who had received broadcast licenses must present "both sides" of controversial issues. This meant that if someone wanted to say that the US Federal Reserve was unconstitutional, one might have to provide an alternative view that it was not.
The Fairness Doctrine worked as well as it did, presumably because World War II vets mostly did not care about these issues for at least two reasons. First, the US "democratic" model had proved itself by conquering or reigning over the rest of the Western world. Second, vets for the most part were interested in reaping the rewards of post-war prosperity. The threat of not returning home had tremendously concentrated their minds and their priorities had to do with family, children and creating a comfortable lifestyle and retirement.
This consensus lasted until the 1960s, when convulsive societal change created considerable cultural evolution. In 1969, the United States Supreme Court upheld the Fairness Doctrine but it ruled that the doctrine was NOT a necessity. This essentially removed the justification for the doctrine; though it took some to die, by 1987 under the somewhat laissez-faire-oriented administration of Ronald Reagan (philosophically anyway), the FCC voted to do away with the Fairness Doctrine. The FCC instead of mandating opposing points of view began to emphasize a diversity of points of view.
There are periodic attempts to reintroduce the Fairness Doctrine, but given the current ferment of ideas and free-market oriented philosophies now present in the United States, it is fairly doubtful that sufficient consensus exists to recreate what many would characterize as outright censorship of the airwaves.