As if to counter the downbeat look at Vietnam veterans airing on public TV tonight, NBC's "Real People" offers its own emphatically upbeat salute to "The American Veteran" at 8 on Channel 4; there is no reason that space shouldn't be made on the air for both views. As usual on "Real People," the film and tape features are extremely well-done and the studio segments, featuring the show's jolly jump-up hosts, are a trifle unsettling.

An appropriate restraint was invoked for tonight's hour, however, and though some of the flag-waving seems shamelessly gooey, just as frequently the program is genuinely touching. Perhaps the best segment is the first, filmed at a reunion of men who served on the USS Lexington in the Pacific during World War II.

There are dissolves from landings of jets on the Lexington's flight deck now to landings of single-prop fighters on the same deck 40 years ago. Old soldiers reminisce about life on the ship; their voices still crack and their eyes still mist when they talk about friends who died there and were buried at sea.

Bill Mauldin narrates some of his old "Willie and Joe" cartoons, a feature on the largely unsung heroics of glider pilots includes a clip from a wartime film about them narrated by young actor Ronald Reagan, and John Barbour visits a teacher in New Mexico who built a chapel in memory of the son he lost in Vietnam. Though not officially recognized, the monument has become something of a shrine to all Americans who died in that irrational war.

A Vietnam veteran, at the site, decries those who call Vietnam an "immoral war" and says, "I have yet to figure which war they had in mind that was moral." Perhaps there were none that were rational, either. This segment ends with Roberta Flack's "The First Time Ever I Saw Your Face" accompanying pictures of dead American boys -- a case of bad taste in a good cause.

One of the most intriguing segments in the program celebrates the contribution to the World War II effort of American Navajo Indians, whose unwritten language proved to be the one code that the Japanese could not crack. Young Navajo marines are interviewed, as are descendants of the "Navajo Code Talkers," whose role has not been widely heralded. A Navajo woman, watching Marine maneuvers from the sidelines, wears a T-shirt that declares, "I Am Proud of My People."

The program then suggests viewers write to President Reagan urging that the efforts of the Navajo code talkers be commemorated with a presidential citation. It couldn't hurt.

What all the segments have in common is the usual dazzle of "Real People" editing, probably the best editing on television outside of commercials. Producer George Schlatter is sometimes so intent on keeping up a breathless pace, though, that certain potentially stunning shots are devalued through underexposure.

At the end of the hour, Sarah Purcell -- the most appealing member of the show's usually chipper cheerleaders -- recites the lyrics to "God Bless America" while standing in Arlington National Cemetery and chokes up on the lines as she speaks them. If this was real, it's quite moving. If this was take 42 for the day, it's still, on some level, affecting. "Real People" should never be confused with "That's Incredible!" or other video freak shows. When it is good, it is is very very good; and tonight, it is good.