The parable of the workers in the vineyard couldn't have happened in modern-day America -- and not just because of the subminimum wage of a penny a day.

Even if the pay scale were adjusted for inflation, the "goodman of the house," as St. Matthew called him, would find himself in trouble as a result of his decision to pay the 11th-hour workers the same as those who were hired first thing in the morning.

State and federal wage boards would cite him for unfairness. The labor unions would attack his multi- tiered pay scales, and, perhaps worst of all, at least one of the workers would take him to court. And win.

A Maryland engineer has just been awarded a sex- discrimination verdict against a restaurant, not because the restaurateur overcharged him but because, as a promotional gimmick, he undercharged women.

Richard Peppin, 43, and a female dined at the Woodside Delicatessen in February 1983. Peppin was charged the regular price for his meal. His companion, because it was Thursday, "ladies' night," got a 50 percent discount. Peppin filed a sex discrimination complaint.

The restaurateur promptly changed his gimmick. No more "ladies' night," he said. Instead Thursday evenings would be "skirt and gown night," and any patron -- male or female -- who showed up wearing a skirt or dress would get the discount. On the very first "skirt and gown night," 10 men, presumably as a joke, showed up in skirts. They got the discount, says restaurant owner Guy Harris. Women who turned up in slacks did not.

Peppin complained again, and managed to convince the Montgomery County Human Relations Commission that "skirt and gown night" was nothing more than a subterfuge for a policy designed to favor females. When a circuit court judge overruled the commission, holding that men who wear pants were merely exercising a "fashion preference," the case was taken to Maryland's Court of Special Appeals, which this week agreed with Peppin and said the Woodside was guilty of sex discrimination.

But perhaps Peppin, having prevailed in court, will forgive me for not applauding his famous victory. I confess that when I first read of the problem three years ago, my response was: problem? What problem?

I know that some of those working to end sex discrimination see "ladies' nights" and other such gimmicks as discrimination, which, if countenanced, could lead to more painful forms of bias. If a "ladies' night" is permissible, then why not a "white night"? Or, if that is too obviously racist, why not "straight hair" night?

Well, it's not the same thing. Restaurant and bar owners have their "ladies' nights" because they believe that if they are successful in attracting more women to their establishments, the men will follow. A special come-on for whites could reasonably be construed as a way of discouraging nonwhites. Specials for women are calculated to produce just the opposite effect. It's discrimination, all right. But so is the senior citizen's discount on city buses; so is a children's fare on airplanes.

It may be that by writing a column on the Woodside affair I am guilty of what I accuse Peppin of doing: making a big deal out of very little. But my argument really isn't with Peppin, who, I suppose, was only standing up for his rights as he saw them. My objection is to an increasingly popular notion that, had it been in vogue 2,000 years ago, might have landed the "goodman" of the parable in court: the notion that every difference in treatment is an injustice, and every injustice deserves redress in a court of law.