You may have seen snippets of this account before, as I have; here, though, is a pretty substantial excerpt, from Fred W. Friendly, The Good Guys, the Bad Guys and the First Amendment, pp. 39-42 (1975):
Bill Ruder, an Assistant Secretary of Commerce in the Kennedy years and an acknowledged leader in public relations, says frankly, “Our massive strategy [in the early 1960s] was to use the Fairness Doctrine to challenge and harass right-wing broadcasters and hope that the challenges would be so costly to them that they would be inhibited and decide it was too expensive to continue.” …
[Arthur Larson, chair of NCCR, one of the groups used for this purpose], who had long been a target of the radical right, recalls his role in the NCCR with embarrassment. “The whole thing was not my idea,” he says, “but let’s face it, we decided to use the Fairness Doctrine to harass the extreme right. In the light of Watergate, it was wrong. We felt the ends justified the means. They never do.” …
In retrospect, [Martin E.] Firestone, now a prominent Washington communications lawyer representing station owners — a number of whom would want him to help repeal the Fairness Doctrine — admits, “Perhaps in the light of Watergate, our tactics were too aggressive, but we were up against ultra-right preachers who were saying vicious things about Kennedy and Johnson.” …
Whatever lessons hindsight has taught, this campaign in 1964 against right-wing broadcasts was at the time considered a success by its creators. In a summary written during the closing days of the presidential election, Firestone pointed with pride to 1,035 letters to stations that produced a total of 1,678 hours of free time from stations carrying McIntire, Dean Manion and Smoot. Both he and [Wayne] Phillips felt a genuine sense of accomplishment.
In a report to the Democratic National Committee, Phillips wrote: “Even more important than the free radio time was the effectiveness of this operation in inhibiting the political activity of these right-wing broadcasts …” In a confidential report to Phillips and the DNC, Firestone stressed the nature of the campaign that “may have inhibited the stations in their broadcast of more radical and politically partisan programs.” … “… Were our efforts to be continued on a year-round basis, we would find that many of these stations would consider the broadcasts of these programs bothersome and burdensome (especially if they are ultimately required to give us free time) and would start dropping the programs from their broadcast schedule.”
So it sounds like the Fairness Doctrine didn’t just have the potential for deterring controversial speech — its users, including its most sophisticated, well-organized, and politically well-connected users, saw the potential and deliberately used the Doctrine for this very purpose. Seems pretty likely that the same thing will happen if the Doctrine were resurrected, though the Internet should make it easy to mobilize many more than 1000 letters of complaint.