Producers Mike and Sonja Gilligan probably couldn't have gotten into West Point if they'd gone there planning to ransack and sully the place. But they didn't, so they did get in, and the remarkably evenhanded and intelligent documentary that resulted, "No Excuse, Sir," airs at 8 tonight on Channel 26.

The film looks dispassionately at West Point, the place it occupies in American mythology, and the military establishment that it symbolizes. The filmmakers went looking for something other than dirty linen; such things as cheating scandals are not even mentioned. Instead, they consider the things that have changed and the things that have stayed the same about West Point in the post-Vietnam era.

Words -- or Haigonyms -- like "internalize" and "prioritize" may be bandied about now, and the ranks of cadets include women as well as men, blacks as well as whites. But the film captures, and the filmmakers respect, the sense of traditionalism and isolationism that mark the place.

Cinematographer Chuck Clifton did a dandy job of falling in love with the location and of finding unaffected but original ways of shooting his subjects. The film is unfortunately much too talk-heavy, but here and there the essential components of filmmaking take over, as when Clifton pans across the valley and its crusty old buildings while the cadets sing their own verses to the "Battle Hymn of the Republic": "intestines were a-dangling from his paratrooper suit," and so on.

Less irreverent and quite moving is a brief sequence later in the film, in which new cadets take their oaths while the camera reads inscriptions on military tombstones nearby: "He perished suddenly and alone; Those who knew his worth will remember him." And, "He left us the buoyancy of youth in the brightness of hope."

Among those interviewed are Gen. Maxwell Taylor and author Joseph J. Ellis ("School for Soldiers"). The final few minutes of the program are a kind of debate on the role of the military in American life; comments of dove Henry Steele Commager are inter-cut with those of hawk Gen. William C. Westmoreland.

Perhaps the documentary should have tilted farther in one direction or the other -- as a portrait of life at the academy, or as a discussion of American militarism, especially now that Reagan is on a defense-spending spree. But having made their decision to mix the two, the producers went on to do an admirable job.

Alas, the program is preceded and followed by gratuitous pedantry supplied by KERA TV in Dallas; the station packaged a group of independently made documentaries for public TV under an umbrella called "Exchange." Something named Tom Grimes comes on to tell us all what we will see and, later, what we have seen; it would have been better to fill out the hour with some pleasant dollop of computer animation. Or a commercial for an oil company.

Grimes refers to John Ford's film about West Point, "The Long Gray Line," as one of the movie hits of "the 1940s." The picture was released in 1955. It would have taken all of two minutes to check.

The title of the documentary refers to what, a young woman cadet says, are the only four responses officers at the academy will accept from cadets: "Yes, sir," "No, sir," "No excuse, sir," and "Sir, I do not understand." In dealing with the clucks of public television, "No excuse, sir," is the one that seems most appropriate.