"The Righteous Apples," a new public TV comedy series aimed at adolescent viewers, may be unassailable enough in intent but it is absolutely excruciating in execution. Even a teenage audience is likely to be too sophisticated not to notice how the program drops pro-social messages like so many lead balloons.

Topper Carew, producer of the program -- premiering at 8 tonight on Channel 26 -- envisioned a situation comedy format that would make those messages entertaining and tasty. The Apples of the title are an interracial rock group in a newly integrated Boston neighborhood who run around righting wrongs and standing up for all that's good and decent in the world.

Also, they each have about as much depth of character as the Pillsbury Doughboy.

In the first episode, they come to the aid of a supposedly adorable old couple who are being held virtual prisoners at a nursing home run by an evil white businessman and his fat hulk of a bouncer -- characters so overdrawn that they are beyond cartoon, much less credibility. One of the program's statements on behalf of old people is that many can still enjoy sex, but the vehicle for this dubious bulletin is a blind ex-musician played with embarrassing cuddliness by Vernon Washington; the character isn't just randy, he's a raving satyriac.

When this old geezer isn't longing aloud for a roll in the hay, he's letting loose with such charming fits of candor as remarking upon the body odor of the woman principal at the Apples' plastic-coated high school. If it takes characterizations this obnoxious to help correct long-standing misconceptions, maybe the misconceptions should be allowed to stand.

The fifth program in the series, also made available for preview and airing next month, attempts to deal at the sitcom level with racial bigotry. The Apples learn that a white racist organization has planned a rally and march on the very night they want to hold a roller-disco dance to raise money for a new synthesizer, and one of their school pals is the son of a rally organizer.

Hmmm. Maybe not every problem and issue in the world ought to be reduced to the sitcom level. Unless it is handled with the finesse and wit of a Norman Lear -- and sometimes even then -- socially conscious sitcommery can come across as frivolous trivializing. Racial bigotry can turn into a mere plot hook on a par with all those roasts housewives kept burning in sitcoms of the '50s, or, more comparable in this case, some new lark for The Monkees or The Brady Bunch.

"Apples" also brings the disreputable spectre of canned laughter to public television, where it ought to be forbidden.

The youngsters playing the Apples are personable enough. Joey Camen, who plays Samuel Rosencrantz, suggests an impish cross between Harpo Marx and Harry Langdon though these qualities are not really exploited in scripts that must keep one eye on the welfare of humanity and the other on making cheap jokes. Watching "The Righteous Apples" -- occasionally more like "The Self-Righteous Apples" -- is like attending a group therapy session or a psychodrama workshop; what if one doesn't feel in need of treatment?

At best, "Apples" is either compromised entertainment or compromised message-mongering. Either way, it is a compromise with which it is not easy to feel very comfortable.