I thought this sort of thing was dead. I thought we had outlived wheelchair gags, pimples jokes and a world in which everything was "spastic."

Granted, such humor is the rage in the sixth grades of the land. Still, I was positive that "sick jokes" would never be used by alleged adults to try to sell a product.

Well, that thud you just heard was Dr. Naive reentering the earth's atmosphere.

In case you missed it -- and mercifully, until the other day, I had -- insulting humor is back on the Washington scene.

Not only is it being used in an ad campaign, but it's apparently a hotcakes success.

The operative word is nurd.

Nurd as in look-at-how-ugly-nurds are (tee-hee).

Nurds as in look-at-how-yukky-nurds'-clothes-are.

And in the case of the recent wave of advertising, nurd as in you'll-never-be-one-if-you-wear-jeans-you-bought-at-The-Gap.

The Gap is a chain of jeans salons where none of the help weighs more than 115 pounds or has been alive for more than 20 years.

Pastel paint graces the walls. Rock blasts from hidden speakers. And peer pressure hangs heavy in the air-conditioned air.

If you are 14, the absolute nurdiest thing you could do would be to wear jeans bought anywhere else, according to Gap ads. It would be almost as serious a crime as forgetting to don your mutilated Adidas tee-shirt or your beat-up Nike jogging shoes.

The Gap has been assailing the airwaves with a "Nurd Campaign" for about the last two months. Like so many ads these days, the "Nurds" are a fast-paced blend of three voices, all exaggerated in the name of satire.

One Gap radio ad, for example, opens with the trembling voice of a nervous mother.

"My son is a nurd," she announces self-pityingly to Voice Two, who is a satin-smooth Gap salesman.

"Come into The Gap," the salesman replies, in his bourbony baritone.

"Thank you," says Ma, as if relief from nurdhood is just a try-on away.

Later, apologizing for her son, who has checked the fit on a pair of Gap jeans by pulling them over his head, Ma says: "Stylish clothes frighten nurds."

This would all be unfortunate enough by itself. But just as life imitates art, radio programming takes its cue from radio ads.

Thus, it was only a matter of time before WPGC, one of Washington's more prominent rock stations, began a Nurd Campaign of its own.

Just last week, WPGC ran a weekend promotion in which its listeners walked in front of a "nurdometer." The contraption registered each person's level of nurdity, to gales of guffaws.

This week, WPGC assembled a panel of prominent people to judge its "Nurd Unfashion Show."

The blurb advertising the show urged people to come dressed as nurds, or to wear what they normally wear. "You might win a prize either way!" roared the blurb's announcer.

To those who would argue that all this is in fun, and that there's nothing wrong with a good laugh, I say: True -- but there are far more respectful ways of inducing giggles.

To those who say that at least The Gap isn't using sex or drugs to entice 14-year-olds, I say: Also true -- but is mockery any safer in the hands of a teenaged kid than lust or pot?

And to those who would accuse me of overstating the case, I say: For every person who thinks it's funny to tell a joke at someone else's expense, there's a butt of that joke who would disagree.

Ask any Pole.

Most copy editors of my acquaintance like to give the impression that they're superhuman.

They like you think that they can write headlines for six stories at once. They would have you believe they know who played second base for the 1943 Brooklyn Dodgers without looking it up. That sort of thing.

Now, from two readers who innocently opened Monday's Post, comes conclusive evidence that a hungry editor is an altogether human animal.

In a story about the Communist leaders' recent get-together in Havana, it was reported that one head of state urged other nations to throw off "the yolk of oppression."

Then, on the sports page, we were told that Dallas Cowboy quarterback Roger Staubach threw the winning touchdown pass against San Francisco "an instant before going down under a blintz."

I can't see why women would want to be "equal" to men in this respect, but . . . .

Lois M. Rodney, of Bowie, reports that in her experience, junk mail aimed at a home with a phone listed under a name whose sex is hard to determine is always addressed to Mr.

"Do you suppose mail computers have been inputted only with male hormones?" Rodney wants to know.