On the surface, the Fairness Doctrine seems like a good idea: if you present a controversial issue, you need to present a fair treatment of the issue and present both sides of the debate. If the public hears both sides of the issue, goes the logic of the doctrine, they can form a better opinion. Furthermore, the argument continues, the fairness doctrine prevents media owners (or managers) from advocating their own political agendas at the cost of public debate.
However, like most public policy, the unintended consequences of the Fairness Doctrine undermine its intended purpose and cause perverse effects that are more harmful than the problem the doctrine was instituted to fix. The two major ways the Fairness Doctrine stifles free speech are 1) opportunity cost and 2) chill of potential prosecution.
Opportunity cost is simply what you give up in order to pursue a given activity. For example, the opportunity cost of me writing this blog is me playing World of Warcraft – the activity I forgo in order to explain the Fairness Doctrine.
In the case of radio shows, there is only so much time in a given radio show (or in a given day if you say the show could just expand to add additional commentary). In order to present a “fair presentation” of an issue (say, the Iraq invasion), a radio host can must cut in half the ten minutes he wanted to spend explaining what a bad idea it was, and give five minutes to a “pro-war” expert. The extra five minutes he might have spent clarifying his point are now quashed.
Furthermore, radio outlets are businesses – there to make money. A radio host once might simply shoot his mouth off for ten minutes about the stupidity of the invasion. Now he must expend the resources to find a “counter point expert” for his show (and pay said expert), resulting in a drier, less appealing (less money making) show. If the alternative is to mouth off about the stupidity of Lindsay Lohan’s latest escapade, needing no additional expert and creating a more appealing ten minutes of commentary, which is he going to choose (at least at the margin)?
Now, look at the station manager’s point of view. If his radio jockey “pushes the envelope” on this, he may have to pay the very real costs of dealing with the FCC. He is much more likely to tell his radio jockeys to “stay away from politics”, and he will choose non-political programming over political programming at the margin. Thus political speech the would have happened absent regulation is quashed.
The function of radio today is not so much to hold public debate; the function of radio is to spark it. The major effect of the Fairness Doctrine is to stifle public debate about issues, since fewer issues can be addressed due to time restraints, fewer people want to listen, and the threat of potential litigation causes risk-averse broadcasters (who are trying to make money) to avoid controversy (at least at the margin).
PS: I did a quick search, and the Cato Institute has a similar article that is likely clearer than mine.