Value judgments bear their own special irony: to use them is to emphasize their undesirability. This is the offense newspapers commit with their habitual reliance on ethnic labels, stereotypes and cliches. They should all be tagged "handle with care."

When former Supreme Court justice Abe Fortas died, The Post wrote that he was the son of a "Jewish pawnbroker." The following day, a story about racial tension in Boston referred to a neighborhood as "white, Roman Catholic."

Most papers, including this one, have policies against identifying race or religion unless the information is relevant. Certainly it was informative that Mr. Fortas' father had been a pawnbroker. It was unnecessary to be told he was Jewish. In a different case, would it read "Gentile" pawnbroker? And, what is the "'Jewish seat'"? This tasteless colloquialism was coined by Washington wiseacres to characterize earlier service by justices Louis Brandeis and Felix Frankfurter. The phrase was in quotation marks, demonstrating that the reporter was not introducing it himself. But why use it at all? Is there a black seat?

In Boston, it was relevant to say the murder occurred in a white neighborhood. It was gratuitous--and possibly inaccurate--to call it Roman Catholic. Does one presume to know that all residents practice the faith?

Stories here and elsewhere concerning abortion frequently refer to Catholics, implying they are the only outspoken opponents. Would the same stories identify a Protestant, a Jew, a Moslem? No. And they shouldn't. Racial and religious identifications have precise meanings, but less relevance to most reporting than journalists seem to assume.

Take, too, the laissez-faire use of those political sawhorses, "liberal" and "conservative." They create at the national and community level as much confusion as a Rubik's Cube--as residents of Takoma Park let The Post know before their elections recently. It was difficult enough long ago to differentiate between Democrat and Republican: one's "liberal" became the other's "conservative." And those who want to retain these political dog tags have taken to books to explain their meanings. Words requiring books to explain them ought to be avoided.

Deputy Managing Editor Richard Harwood, first occupant of this chair, once challenged Post editors to parse in 20 words or less the meanings of "liberal" and "conservative." That was 12 years ago. To this day, he's had no response. Before then and since, they spawned their own mutations--"hawk," "dove," "neo-liberal" and "neo-conservative." Daily newspapers should treat these bastards of speech as if they were libelous. Maybe they should be.

Mindless use of stereotypes is a form of what Walter Lacqueur calls "psittacism--the habit of using words without thought," one better left to parrots than journalists. It may be that more thought is invested than users get credit for. But thought is no guarantee of clarity. Recently, for example, reams of news space have been given to delineating the difference between "recession" and "depression." Yet, beyond conveying a sense of fright about "depression," most of us have difficulty understanding what makes one distinct from the other.

Interchangability of terms comes at us also from abroad--as with "revolutionary," "guerrilla," "terrorist." All could be someone else's "freedom fighter." There's "activist" and "militant." The press generally sees the former as the equivalent of someone in "white hat," the latter in "black hat." You get the picture if--as has been the case--one is identified as a "militant activist."

Not all this word coinage is journalese; governments also contribute.Whoever fully understood "d,etente"? Not even President Ford who, trying to erase it, made it more of a story. More reason, then, for the press to be discriminating with readers.

Now, just when I thought "hippie" and "hard hat" had been committed to final resting, they made their dumb way back into these pages recently. You won't find "hippies" and "hard hats" keeping company the way old clich,es and stereotypes go steady. If only familiarity would breed some contempt. That fictional editor who cried, "What we need are some new cliches," died sadder not wiser, leaving the matter easier said than done. He was not the one who thought "cliche was a suburb of Paris." In a profession that still cannot agree on a common definition of what is "news," you get some idea of the problem.