The accomplishment of "Central America in Revolt," a 90-minute CBS News special at 9:30 tonight on Channel 9, is that it helps one comprehend why the problems and traumas of Central America seem incomprehensible. It is a sturdy, depressing and perplexing report, part of a weekend of CBS News coverage of the crucial and chaotic region that will continue with a special edition of "Face the Nation" at 11:30 Sunday morning.

"Revolt" divides up the most troubled countries among top correspondents. Bill Moyers reports on El Salvador, Mike Wallace on Nicaragua, and Ed Rabel on Guatemala. Moyers returns for a situationer on Mexico and joins anchor Dan Rather to look with lavish sobriety at American policies.

In El Salvador, no one has been tried for murder since the '60s, Moyers reports, though not for lack of victims. He interviews a woman who is nursing her baby and recalling the day troops took away her husband-- a scene more than mildly reminiscent of the current movie hit, "Missing." Elections are coming to El Salvador ("El Voto!" says a poster), though there is considerable skepticism about their legitimacy. A government official tickles Moyers--rather than reassures him--when he describes a device for preventing repeat voting: the dread "inky pinky."

Deane Hinton, the U.S. ambassador to El Salvador, has previously proven a refreshingly gruff subject in other interviews. He says the rebels in the hills want to mete out not reforms but "pure Marxism," but he also concedes there are "some pretty tough, disagreeable bastards" in the government the United States supports there. "They're not all boy scouts on the side we're supporting," Hinton says. "The world is more complicated than that."

In Nicaragua, Wallace talks with a Roman Catholic nun who rides a motorcycle and has found herself allied in the revolution with, among others, a Cuban Marxist. She thoughtfully quotes for Wallace the line from the Nicaraguan national anthem that says "We're fighting against the Yankees, the enemy of humanity." Rabel's report from Guatemala and its "widening civil war" includes footage CBS bought from an "independent" film crew and the observation that in this country, "Elections are little more than negotiated settlements among groups of right-wing politicians."

There is more reliance on talk than on pictures in the program. The least persuasive talk, other than the hollow blusterings of senators heard in the final act, is an American businessman's contention that in Guatemala, oppression does not exist, is "just something that some reporters have thought up," though Rabel reports a little later that Amnesty International has called Guatemala "the worst violator of human rights in the Western Hemisphere."

Also worth an audience, on the other hand, are the allegations of U.S. Ambassador to the United Nations Jeane Kirkpatrick, who says American press coverage of Central America has "not been good," and that "I think CBS has been particularly bad, if I may say so. I think . . . The New York Times and The Washington Post, and CBS have been really pretty major offenders in . . . what I would consider inaccurate coverage. I think they suffer from the Vietnam syndrome . . . that there is a kind of Vietnam hangover which makes them predisposed . . . to disbelieve the U.S. government."

The most persuasive words are those of Carlos Fuentes, Mexican writer and political scientist, and a dynamic figure, who speaks of "giant historical mistakes" made by the United States in Central America. "This is a sorry sight," he says, "the way you lose friends in Latin America." There seems widespread agreement that much of what the United States has done is wrong, tactically if not morally--but no one interviewed on this broadcast, not even the walking conscience Bill Moyers--seems to know what would be right.