Not all is whimsical within "The Whimsical World of Oz," a highly suspect PBS special at 9 tonight on Channels 26 and 32 and the Maryland Public Television stations. Ostensibly a review of the widely beloved Oz books by L. Frank Baum and the subculture they've engendered, the program shifts tone midway and turns into blatant promotion for the upcoming Walt Disney film "Return to Oz."

Public television should not be the place for prolonged promotional binges, whether the Reagan administration is cutting its budget to bits or not.

Rushing madly through the first 80 years or so of Oziana, the program allows for mere snippets of remarks from Ray Bolger (lying down, for some reason), Ray Bradbury, Erica Jong (who praises the "terrific women" Baum invented in his stories) and a few of Baum's descendants. His granddaughter says she was terribly uncomfortable with the name "Ozma," bequeathed in honor of a character in the books, "so I changed my name to 'Scraps.' " Naturally.

Much of this material, including scenes from early silent film versions of the Oz books (MGM's 1939 "The Wizard of Oz" was actually the fourth film version), is amusing and engrossing. But people come and go so quickly here! They are all shuttled out of the way so the program can consider at great length and much slower tempo the forthcoming Disney production.

It will be "a unique motion picture," breathlessly promises narrator Mason Adams, with "spectacular sets," all painstakingly examined and extolled. The little girl who plays Dorothy this time says, "I did all my own stunts." The slickness of the program, and the generosity with which the Disney film is plugged, are reminiscent of program-length commercials masquerading as featurettes that commercial stations air prior to movie openings.

Yesterday John McKinley, assistant director of acquisitions at PBS, said the program does not constitute promotion for the Disney film and that he thought the footage shot on the set of the Disney movie was "absolutely lovely" and should have been included at the opening of the program "as a tease." A tease is a device commercial stations use to grab viewers lest they consider changing the channel.

"We didn't see anything that was crassly commercial," McKinley said of the program, a product of Production Associates of England, where the Disney movie was made. "We did not perceive it as a plug. It's unfortunate that it can be construed as such." He said that to his knowledge Disney contributed "absolutely nothing" to the production costs of the program. McKinley also said he didn't understand how the program could be thought of as promotion since public TV stood to gain nothing by it.

L. Frank Baum created wonderful, wacky, kooky, nutty characters, but it's doubtful even he could have fashioned a magical land as loonily inscrutable as the whimsical world of public television. For a viewer, the solution is to watch the first half of tonight's program and skip the polluted and zealously promotional second half. 'Right to Kill?'

A night without a psychopath is like a night without prime time. Tonight ABC once more delves into its bottomless file of newspaper clippings for another fact-based exercise in domestic hysteria, "Right to Kill?," an "ABC Theater" presentation at 9 on Channel 7.

The film, written by Joyce Eliason and directed by the overrated John Erman ("A Streetcar Named Desire"), is based on the case of Richard Jahnke Jr., a 16-year-old Wyoming boy who ended his father's reign of abuse on himself, his mother and his sister by murdering him with three blasts from a shotgun. The way one can tell ABC is serious about this latest in its current series of Ghastly True-Life Tales is that no glamoroso figures like Cheryl Ladd have been cast in any of the main roles. Some of the actors are authenticatingly plain and dumpy.

Director Erman seems to be trying to edge the film into a tract against gun ownership. The abusive, vicious father keeps a cache of weapons at home, and when his son (Christopher Collet, an appealingly unpolished young actor) is 37 minutes late home from a date, Dad greets him with a revolver at the top of the stairs. The film ends with reprise of a scene in which the son got the rifle from Dad as a birthday present.

According to ABC publicity, "Everybody involved with 'Right to Kill?' felt responsible for telling the true story of what happened . . . without condoning the action of the abused teenager who shot his father to death." However, Erman, interviewed on "Entertainment Tonight" recently, said he made it clear in the film that the son's action was justified. So much for objectivity, though objectivity would probably be a trifling virtue anyway in this kind of sensationalistic undertaking.

On one level, the film works: as a docudramatic version of "The Shining," a failed horror movie about the effects of isolation on a warped mind. Frederic Forrest, as the father, is already deranged when we meet him, but there is a certain primal power to his accelerating madness. The relationship between the son and his sister (Justine Bateman) is touchingly desperate as well. But this doesn't seem enough to justify another two hours of horrific domestic violence on the home screen, and calling it "theater" is but a sick sort of joke.