The story of the gay and lesbian movement over the past three decades has been one of advances and setbacks, but no retreats. "After Stonewall," a 90-minute documentary airing at 9 tonight on Channel 26, chronicles the era in a rather cut-and-dried but admirably comprehensive way.

Producer-writer John Scagliotti had a lot of material to cover, but he seems to touch most of the bases that need touching. The eventfulness of the years since Stonewall--a landmark riot that broke out when cops tried to raid a gay bar in New York--virtually requires that the film move along at a rapid clip, and indeed it does. The clips come rapidly.

Is there a reason to watch if you think you have no vested interest in the subject? The film implicitly makes the case that anybody who cares about equality for all has a stake in the dreams and desires of gay people. Writer Armistead Maupin touches on this when he recalls of his own leap from the closet, "I began to reexamine all my prejudices."

Scagliotti opens with a clip from the nasty cable cartoon "South Park," in which one of the hideously drawn tykes declares, "It's okay to be gay." Is this progress? Well, it's hard to imagine Bugs Bunny ever saying that. Soon we see two men in white tie and tails getting "married" in a ceremony mimicking the heterosexual equivalent. Is this progress? The filmmakers seem to think so--but they deserve credit for not being overly preachy or didactic.

Stonewall spurred actions of affirmation by gay men and women all over the country, and eventually the world, and the film looks back at the emergence of groups like the Gay Liberation Front, the Gay Activists' Alliance and a latter-day organization colorfully called Lesbian Avengers. But other groups emerged, too, in a backlash that often grew virulent, starting with Anita Bryant and her "Save Our Children" group (she seems to have confused homosexuals with pedophiles).

Allegedly religious figures like Jerry Falwell called for hatred and fear, and New York's Cardinal John O'Connor used the pulpit to preach bigotry. Ronald Reagan said he couldn't accept the idea of gayness as "an alternate lifestyle," and a gay activist complains that Reagan was so well liked and critic-proof that effective protests could not be mounted against him. At least he never lied to gay groups, as President Clinton is accused of doing with his "gays in the military" campaign.

Among those heard from, in addition to Maupin, are Rep. Barney Frank (D-Mass.), who talks about his decision to come out; writer Larry Kramer; New York City Council member Phil Reed; and Sheila James Kuehl, who was a lovable child star on TV's "Stuart Erwin Show" and "Dobie Gillis" and is now an openly lesbian member of the California Assembly.

And still lovable.

We also see, briefly, film of Matthew Shepard, the young man murdered for being gay in Laramie, Wyo., last October. And, as a further reminder that hatred still thrives in America, we see a sign carried by a protester at his funeral: "No Fags in Heaven." What kind of person ventures out on a cold, snowy day and intrudes on the grief of family and friends to spread such poison?

AIDS is, of course, a large part of this story. A bell sounds ominously on the soundtrack when the subject first comes up, back when the disease was considered a new strain of cancer and wasn't even known to be sexually transmitted. Then comes the death of Rock Hudson, which, however sad, put AIDS on the front pages of the world--five years, and 5,000 American deaths, after it was first observed.

Footage of demonstrations becomes repetitious, and they all seem to blur together. Even sympathetic viewers may have their doubts about a young man who says, "I'm proud of it, to be HIV-positive," or when the AIDS epidemic is implicitly compared to the Nazi Holocaust. But then perhaps Barry Goldwater wasn't being so "extreme" himself when he said--in a different context, of course--that extremism in defense of liberty is no vice.

Subaru and Citibank deserve plaudits for bravely being the two main corporate underwriters of the film, especially since Falwell may come swooping down on them as enemies of decency and goodness and all that sort of thing.

"After Stonewall" has little original imagery and suffers from an excess of talk, but at the end of the day--which is when it airs--it gets the job done and proves the job worth doing.

CAPTION: Longtime activists Barbara Gittings, left, and Kay Tobin Lahusen.