Expatriate viewers who drop in on television only to witness a rare special event - and then find the event an enormous disappointment - are like citizens of a republic who haven't voted in 30 years and then, upon entering the voting booth, become horrified by the caliber of the candidates. They have a right to complain but their previous abstinence makes their objections irrelevant.

Commerical television programs are produced for the regular television programs are produced for the regular television audience. It only makes sense; newspapers tend to be aimed at people who read newspapers. When an unusual TV attraction draws large numbers of occasional or nonviewers, they should remember that they are strictly a supplemental audience, and not the one that the networks have promised to deliver to advertisers.

And being unaccustomed to the rhythms, textures and standards of television, they are likely to find inadequate that which regular viewers may be hailing as a godsend.

"Holocaust," NBC's four-part program on Nazi persecution of the Jews, was hardly an esthetic masterpiece or a paragon of dramaturgy, "docu" or otherwise. But it was a great shared experience for the viewing nation the way "Roots," another triumphant mediocrity, was last year. What matters is not what those already expert on the Holocaust and its significance think of the television program - because they are a select group, not the shows mainstream target - but rather how it penetrated the national consciousness.

Figures, failible though they be, indicate it penetrated very well. The fact that people watched in increasing and enormous numbers over the four nights (as many as 120 million people in all, according to admittedly optimistic NMC Research) suggests the American TV viewer is made of s terner stuff than might have been assumed from previous habits and an apparent devotion to fluff.

To judge either "Holocaust" or "Roots" in a vacuum, without considering the audience for which they were intended or comparing them to regular TV fare, is folly and not at all conducive to encouraging further treatments of difficult material on television. If "Holocaust" had been flagrantly callous and exploitative, that would be cause for alarm, but lit wasn't. It towered like a skyscraper on the vast flat plain of TV programming.

Some have said that the subject matter is not fit for TV dramatic treatment. That leaves two alternatives: Surrender all, not just most, of TV to the fluff packagers, or make a documentary on the subject that almost no one will watch.

Any work that is primary television - that is, made for TV - has gone through more compromises than any movie, play or book, because the economic stakes are greater. The encouraging thing about "Holocaust" is that the compromises did not prove ruinous and that what remained often scored with devastating effect. Were the walls of Auschwitz too clean? Were the uniforms of the prisoners too tidy? Were the extras not sufficiently emaciated? No one familiar with television could have expected an unblinkingly realistic depiction, but anyone familiar with television should have seen that there was more grim truth here than is usually permitted to meet the eye.

NBC's Paul Klein occasionally trots out his arena theory of network television to explain why a performer who can fill 18,000-seat auditoriums may get lousy ratings on television. TV is a bigger areana. It doesn't mean the performer has flopped only that he or she was meant for a smaller arena. "Holocaust" was designed for the biggest arena of all, the prime-time network television theater, and so to expect it to have the finesee, the subtleties or the beauty of a literary or motion picture "classic" is unreasonable. In an arena of this size, such qualities may be largely lost anyway, the way a folksinger's delicate shadings might be lost on most of those in the audience at a Superdome.

In this sense, TV can be seen in negative terms as the relentless homogenizer, or in positive terms as a populist forum than can make once-privileged information available to all. Uusually, it doesn't bother with information that matters. With "Holocaust," it did.

It would have been futile, in years past, to have criticized Life magazine for not attaining the rarefied literary tone of The New Yorker. Different audiences for different arenas. It would be nice, of course, if television, with its largely untapped capacity for diversity of choice, had reserved a little corner to be The New Yorker of the air. The logical hope was that public television would fill that bill but unfortunately it developed more along the duller and less adventuresome lines of the Saturday Review. But that's another problem.

Gerold Green's script for "Holocaust" was indeed riddled with misjudgments and clumsiness, but what counts is the total work and the total effect. One complainer said that only one out of three scenes in "Holocaust" really registered with authority and conviction. That may be true, but the complainer was a nonviewer. He didn't know that for television, one out of three is a fantastically high ratio.

Some who criticized the depiction of Nazi horrors as not being horrific enough probably would not be satisfied with anything less than a film so horrific that no one would be able to watch it a hollow victory for realism. Unquestionably, the images of suffering and degradation did have tremendous emotional meaning for millions of people unaccustomed to such disturbing material on television. "Holocaust" joins "Roots" and "The Autobiography of Miss Jane Pittman" and documentaries like "Harvest of Shame" in defying TV's traditional, lulling, portrayal of the world and the human race. Such programs commit the heresy of raising questions that can't cozily answered by 11 o'clock. They run counter to the television doctrine of keeping viewers happily pacified and thus receptive to commercial messages.

That is the prevailing doctrine, as Erik Barnouw notes in his new book "The Sponsor; Notes on a Modern Potentate." Barnouw quotes ABC-TV executive Bob Shanks on what is proper television entertainment:

"Program makers are supposed to devise and produce shows that will attract mass audiences without unduly offending these audiences or too deeply moving them emotionally. Such ruffling, it is thought, will interfere with their ability to receive, recall and respond to the commercial message. This programming reality is the unwritten, unspoken gemeinschaft of all professional members of the television franternity."

Shanks is now working on ABC's upcoming TV news magazine, "20/20."

"Holocaust" did move people emotionally, perhaps too deeply for them to be receptive to the commercials - deeply enough, at any rate, for many to find the commercials incredibly repugnant. Viewers may have seen the same commercials countless times previously on other programs, but these were programs designed to be unruffling. In this respect, "Holocaust" may have performed, albeit unwittingly, another service to viewers. It gave us a disquieting new perspective on the vulgarity and intrusiveness of TV commercials - on the kinds of messages endlessly delivered and the frivolous uses to which television is usually put.

People who hate television, or who feel the only defense against it is not to watch it, and are using the short-comings of "Holocaust" as further proof for their case, might be surprised to find the program having a viewer backlash effect more significant than that induced by their own indignant rhetoric. If "Holocaust" dealt in part with what has been called "the banality of evil," we came away from it not only shaken by the subject matter but also by the fact that most of the time, television's great concern is the banality of banality.

Three of the most commonly heard words in the American television home today are these: "There's nothing on." We say those words in that order often; and yet we turn the TV set on anyway and watch whatever seems, in Klein's immortal phrase, "least objectionable." For four nights last week on NBC, THERE WAS SOMETHING ON, and thinking back on it may affect for some time the way we look at television and what we have let it become.