Well, it did happen. When CBS canceled its announced program to set the facts straight concerning its controversial Westmoreland documentary (''The Uncounted Enemy: A Vietnam Deception''), it was clear what was happening. Since General Westmoreland was preparing to sue CBS, it made little sense from the network's point of view to provide him with further ammunition in advance of the lawsuit.
Shortly after that, the general announced that he was filing a libel suit for refused to accede to his demands for, among other things,''a full retraction of not less than 45 minutes to be broadcast as widely at the same time and day of the week as the original report . . . subject to my complete approval.''
The original program, which aired Jan. 23, 1982, accused the general of taking part in a conspiracy to deceive the President and the American public by underestimating the strength of the Vietcong so that determination to wage the war would not wane. The general denies that accusation.
Van Gordon Sauter, president of CBS News, responded to the Westmoreland announcement by saying that ''CBS will wage a vigorous defense, not only because we see this suit totally devoid of merit, but because it constitutes a serious threat to independent journalism in our society.'' Although an in-house CBS News report allegedly found that certain internal procedural rules were broken in the preparation of the documentary, Mr. Sauter said ''we stand by the broadcast.'' He reiterated CBS's offer of a 15-minute unedited statement of the general's position.
Meantime, makers of TV documentaries on all networks are scrutinizing their accusations just a bit more carefully in order to face the barrage of network lawyers who are working overtime to make certain that libels do not slip through to the air. One can only hope that this wariness will not result in a total blackout for tough investigative reporting.
On another CBS front, it was announced that CBS Cable, one of the most highly praised cultural services on cable, will cease operations within 90 days. So for many cultural events, it will be back to PBS, where viewers (and underwriters) appreciate what is available free.
''Live From Lincoln Center,'' a PBS standby for many years, never made the transition from PBS to cable so, according to Lincoln Center officials, it will continue free on PBS as in the past . . . at least for a while.
One of CBS Cable's most successful original series, ''A Walk Through the 20th Century with Bill Moyers,'' which premiered on CBS Cable two weeks ago, is now available for airing elsewhere. PBS president Lawrence Grossman told the Monitor he would be very pleased to have it on PBS. However, with CBS News in a credibility crunch because of the Westmoreland libel suit, it is possible that CBS News, too, may now be interested in airing the superb 20-weeks series. Bill Moyers on the CBS Evening News has proven to be a major draw, helping Dan Rather keep the show in the No. 1 network news position.