Fred Friendly wants Americans to get to know their Constitution

''The Willy Loman of the Constitution'' bursts into his spacious office at the Columbia Graduate School of Journalism, dictating a letter to his secretary. ''To Charles Kuralt at CBS,'' Fred W. Friendly says, as the waiting interviewer eavesdrops shamelessly. ''I heard your essay on cheese the other day and I realized once again that you are one of the best writers on television....''

On the wall is a sign that reads: ''Difficulty is the one excuse that history never accepts.''

Mr. Friendly, former president of CBS News responsible for the development of Edward R. Murrow's ''See It Now'' and ''CBS Reports,'' former communications adviser to the Ford Foundation, is now Edward R. Murrow professor emeritus at Columbia. He is also senior program adviser for the Media and Society Seminars, from which stemmed the current Annenberg/CPB Project, The Constitution: That Delicate Balance (PBS, Tuesdays, 10-11 p.m., check local listings for premieres and repeats), for which he serves as commentator.

Mr. Friendly is a tall, lanky, yes friendly man who looks a bit like Gary Cooper crossbred with Big Bird. He somehow manages to combine a laid-back professorial demeanor with the crisis air of a television producer. Certainly, when he talks about ''The Constitution'' television series, the relaxed attitude is replaced by a burst of excitement and enthusiasm.

At the slightest provocation in any discussion of the United States Constitution, he has been known to distribute little blue-covered copies of that document. That's why he jokingly refers to himself as ''The Willy Loman of the Constitution,'' always selling. He chuckles amusedly when I suggest there's a bit of Johnny Appleseed in him, too.

''The Constitution: That Delicate Balance'' is a 13-week series now in its sixth week, which uses the Socratic method (''we also borrowed a bit from Phil Donahue'') to create hypothetical situations that test the limits of the Constitution. Moderators provoke the participants into spontaneous reactions, then confront the implications with balanced logic. Not only does the viewer see the participants think, the viewer is encouraged to think for himself as well. More than 200 schools are using the series as the basis for a credit course.

What would constitute success for the series in the opinion of Fred W. Friendly?

''More consciousness of the Constitution on everybody's part. Our goal is not to make up people's minds for them, it is to force them to think for themselves about hard choices.

''I want to help make the Constitution a vernacular document - which lives in the mind of the guy at the toll gate as well as in the minds of the members of the Supreme Court. It has to have meaning in Hoboken, N.J., and Eugene, Ore. If we all don't understand it, then it is just a piece of paper that you can put away like a high school diploma.''

Friendly feels strongly that the current CBS-Westmoreland trial should be televised. ''Journalists keep saying there is a constitutionally guaranteed right to know. Well, there is a need to know but in my copy of the Constitution I cannot find a right to know.

''The courts have never said that the media is beyond all the restraints. You cannot restrain a newspaper from printing unless it involves something like troopships sailing in time of war. But you can always sue for libel.

''Well, General Westmoreland is suing for libel. He has a very big burden to prove: first that what was said was false and then that it was done with the knowledge that it was false. A very hard thing to prove.

''I'm sorry (the trial is) not on television because, aside from people seeing it every night, the documentary, which could come out of the tapes, could be far better than the original CBS Report on Westmoreland. They could do a 13 -week series that would demystify both the military and broadcast journalism. Wouldn't it be nice if all wars could be fought in court rather than on the battlefield?''

Friendly feels the trial has already had a chilling effect on journalism. ''The extent of it we will have to wait to see. But it may have some value if it makes journalists more wary about carelessness and arrogance.''

Mr. Friendly, however, does not feel that the chill is responsible for a diminished number of network news documentaries. ''The real reason for the shortage of news documentaries is the high cost of air time. Networks can sell amusement entertainment for $150,000 a minute as against $30,000 for documentary time.

''Edward R. Murrow once said to me: 'The darkest day in television will come when news becomes a profit center.' Now this has happened with '60 Minutes,' which has proved that you can make money with amusement news, instead of good, hard news programming. If you watch '60 Minutes,' you'd never know there is an election going on.''

Mr. Friendly also holds an antagonism toward the TV docu-drama form. ''It scares ... me. Murrow and all of us in TV news worked very hard to maintain that line between reality and make-believe. I even hated 'You Are There.' People who watch docu-dramas often don't know whether they are watching truth or fiction. And often it is a mixture of both. That's dangerous.''

Edward R. Murrow is often mentioned by Friendly. ''In a famous speech he made in 1958 he said that this instrument of TV can entertain, illuminate, inform, inspire. But only if mankind is willing to use it for that purpose. Otherwise, it is just lights and wires in a box. If he were to come back now and turn on a television set, he'd find that it is just lights and wires in a box.

''Probably the last chance is Public Broadcasting. Do you realize what marvelous entertainment/information programs are available on PBS this season? There's 'Heritage' and 'The Brain' and 'The Constitution!' ''

Suddenly, Friendly - shifting back to the issue that most occupies his thought these days - says:

''My hope is that the Constitution bicentennial celebration in 1987 can be more than marching bands and fireworks. I hope it can be a substantive dialogue about this important document. There are Bibles in every hotel room - I would like to put a copy of the Constitution in every living room.

''What I would really like to see is local TV stations all over America repeat 'The Constitution' series, stopping as they go to allow local lawyers, ministers, citizens to play the same game as we do on the series.''

Mr. Friendly seems to take as his motto something his wife once found on a classroom blackboard: ''My job is to make the agony of decisionmaking so intense that you can escape only by thinking.'' Within those parameters, his series, ''The Constitution: That Delicate Balance,'' is an exquisite agony.