BEWARE THE SCHIZOID TUBE

Call it television’s dominant and recessive voices; call it the medium’s superego and its id. (Hell, call it Heckle and Jeckle for all I care.)

In its normal voice, TV is unfailingly polite to its audience, which makes a lot of sense considering that the audience is what TV sells to its sponsors and is therefore TV’s real product.

Yet every so often there is that other voice, that other persona, the one that rivets us, startles us, commands our attention precisely because it is not so nice. In fact, it can be downright nasty.

Those of us old enough to remember television’s earliest days heard it in the voice of Ernie Kovacs, the mad jester of the black and white screen. In the early ‘50s, variety show hosts never signed off without saying to us sincerely, “Thanks so much for letting us into your home.”

One night, Kovacs looked out and said, “Thanks for letting us into your home--but couldn’t you have cleaned it up a bit?”

Talk about a bucket full of cold water in the collective face of the audience!

Right now, nobody does it better than David Letterman, who exults in taking a camera through the streets of New York City, pointing out spelling errors in the homemade signs of shopkeepers. A more sensitive soul might pause at ridiculing people who work 16 hours a day for not much money, and who frequently speak English as a second language. For Letterman, it’s all grist for the humor mill.

As for sensitivity to his audience, it was Letterman who taped a promotional spot that said, “Here at NBC, you’re more than a number, you’re--no, actually, here at NBC you are a number.”

Letterman, of course, is standing on the shoulders of the 12-year-old “Saturday Night Live,” the program that brought National Lampoon’s take-no-prisoners sensibility onto the screen.

(Who could ever forget the song, “Let’s Kill Gary Gilmore for Christmas,” performed as the condemned murderer was awaiting execution?)

But, in his break with the Emily Post school of TV etiquette, there are small but unmistakable signs Letterman is not alone.

On the new Fox Television Network, the Sunday night sitcom “Married--With Children” features a couple light years removed not just from “Ozzie and Harriet,” but from “Cosby,” “Valerie,” “Growing Pains,” “Family Ties” and all those trendy but lovable families of today. The insults hurled across the Bundy living room are really designed to draw blood.

More astonishing, even commercials--those ultimate acts of video pandering--have their practitioners of the raspberry. For example, the smarmy Joe Isuzu finds his patently outrageous claims for his car cruelly contradicted by the words that appear below him; they simply proclaim, “He’s lying.” And look at the grotesque figures in the commercials for Federal Express, Wendy’s, Alaskan Airlines, and the other products that at one time were all handed over to the tender mercies of ad man Joe Sedelmaier.

Every single one of his people is burdened with a triple chin, an enormous beer belly, a nose the size of a cucumber, or similar appendages. The only less-appetizing collection of “typical” folks can be found in the works of Hieronymus Bosch.

But what about that tag line for Grape Nuts that declares, “The question isn’t whether Grape Nuts is right for you; the question is whether you’re right for Grape Nuts”?

But for sheer, unadulterated nastiness, it’s going to be hard to top the ad campaign for BVD underwear, featuring the ultimate symbol of TV nastiness, Larry (J.R. Ewing) Hagman. After besting his competitors in a nefarious business deal, he sneers to them--and the announcer warns us--”Isn’t it time you changed your underwear?”

No doubt about it: Nastiness on the tube is a clear, if minor, trend.

You don’t think so? That might bother me if I didn’t know a hell of a lot more about television than you do.