IT APPEARS THAT CBS has caved in to the complaints shouted by friends and supporters of Ronald and Nancy Reagan, who claim that the network's upcoming miniseries about the famous couple is more fiction than fact. Predictably, CBS's canceling of the show has led to cries of censorship and fears of a "chilling effect" on free expression.

In such a charged climate, it bears remembering that network television has a long history of capitulating in the face of threatened boycotts by both sponsors and the general populace. Such "censorship" is, in fact, as old as the medium itself.

Here's one story, from television's so-called "Golden Age" of live television drama, that makes the current situation seem as silly as the networks' onetime edict against using the word "pregnant."

IN EARLY 1956, TV writer Rod Serling wanted to tackle the case of poor Emmett Till, a black 14-year-old Chicago boy who on a visit to Mississippi the previous summer had made the fatal mistake of whistling at a white woman. When the two rednecks who'd kidnapped and killed him were acquitted by an all-white jury, Serling approached the producers of ABC's "The United States Steel Hour," for which he'd already written several well-received scripts.

Sensibilities were too raw to use the real names and circumstances, so Serling transformed Emmett into an elderly Jewish pawnbroker who "dies at the hands of a neurotic malcontent who is in turn tried and released by his own neighbors." It was, Serling wrote, "The story of a town

Before "Noon On Doomsday," Serling had previously suffered a head-scratching run-in with network censors on his "Studio One" drama called "The Arena," about the United States Senate. (It seems the guys with the blue pencils would not allow any senator to say anything that might remotely be identified as coming from the political right or left.) But what could possibly be controversial, Serling asked, about dramatizing the evil of lynching? Who was going to be offended? The lynchers themselves? Apparently. Soon came word that the network and sponsor demanded wholesale changes in the script.

WHAT'S IMPORTANT TO UNDERSTAND HERE is that no writer was more important to television in the 1950s than Rod Serling. For five years before he became synonymous with "The Twilight Zone," Serling's thoughtful dramas dominated the medium, and he himself dominated the dramatic writing Emmys. His 1955 script (for "Kraft Playhouse") "Patterns," about corporate corruption, was the only live show ever to be brought back by popular demand for an encore performance. Similarly, his "Requiem for a Heavyweight" was television's first original 90-minute drama, and launched CBS's "Playhouse 90," where he became a sort of writer-in-residence for the next three years.

In those days, entertainment reporters often wrote about television scripts still in rehearsal, and when an otherwise innocuous dispatch about "the story of the Till case" drifted into the South, the White Citizens Councils threatened a boycott of U.S Steel. (Serling asked whether their buildings would now be constructed of aluminum.) Soon, Serling's pawnbroker had become "an unidentifiable foreigner" and the murderer "a decent kid momentarily gone wrong." ABC even removed a Coca-Cola sign from the set of a diner, believing that it too clearly evoked the South. Meanwhile, the word "lynch" was excised and every character spoke with diction worthy of Henry Higgins--perfect for the New England backdrop. Serling joked darkly that they would've chosen the North Pole as the script's location were it not for the pesky problem of another minority group--Eskimos.