HALF OF US weren't born in 1950 when the rogue elephant, Joe McCarthy, set out to trample the Red Menace in our society. He was a member of the United States Senate, the chairman of its Permanent Subcommittee on Investigations, an insatiable, conscienceless publicity addict.

The time was right. For five years we had been on a Red binge. We had committees of Congress defining unAmerican activities. There were loyalty oaths, security investigations, official listings of subversive and sort- of-subversive organizations, black lists and dossiers by the millions. Even the Tennessee legislature smote at the devil with a proposal to require patriotic swearings from cab drivers in exchange for state licensing.

Through those years of slander and fear, many American newspapers had a grand run. "Reds" was the story of the decade. Investigative reporters sought them in schools and labor unions and churches and within the ranks of journalists themselves.

The general manager of The New York Times voted for a purge of ex- communists in his newsroom. "Ten Nights At a Communist University" was a hot series in The New York Post. In Southern Indiana, a henpecked Slav with a radical wife was discovered in an Army quartermaster depot knocking dents out of damaged mess kits. He had a choice: Give up his "subversive" spouse or his job. It was a front-page sensation.

McCarthy rode this wave into the 1950s, nourished by publicity and booze. Edwin Bayley, one of the historians of the era, has written that in McCarthy's own mind his purification "crusade" was part hoax -- a political game. Murrey Marder of this newspaper understood that early on and later told Bayley that McCarthy was essentially "a mischievous child. He didn't give a damn about communism or anything else. It was all a game with Joe." And it was damned good copy.

In the McCarthy aftermath, soul- searching among editors, reporters and publishers became fashionable to the point of tedium. Why had they played Joe's game? What might they have done differently? A common conclusion was that newspaper "objectivity" ought not be carried to mindless extremes, that it was not enough to report accurately the charges and allegations of every fool and charlatan in public or private life.

The rights of suspects and defendants should be honored. Charges should be weighed and examined before the shot is fired. The actions of government agencies, political figures and accusers of whatever standing should be subject to the inquisitive skepticism we presumably apply to tales of Second Comings and Loch Ness monsters.

There was a bit of self-absolution in this searching of souls and a bit of self-delusion, too. Boy Scout oaths, with however fine a ring, could not exorcise nor alter the nature of our trade. The essence of the news business is not ultimate truth, although we may stumble on it from time to time. Rather we produce, in the familiar phrase, rough first drafts of history. The do not, in every case, stand the test of time.

We find it particularly difficult to handle the conspiratorial spasms that infect our public affairs -- who killed Kennedy, who lost China, who slept and why at Pearl Harbor, who runs the Capitol Hill "dope ring," are Hitler's diaries real? These long-running dramas are products of the investigations industry which deals with the unknown and sometimes with the unknowable.

A senator, a prosecutor, a committee or a grand jury launches a search for 57 communists in the State Department, a malefactor in the White House, moles in the CIA or whatever. The newspapers tag along, one step behind, rarely knowing whether gold or garbage lies at the end of the trail.

In recent years, the press has taken several fruitless journeys in Washington with special prosecutors. There was the protracted investigation in 1976 of President Gerald Ford's use of campaign funds, an investigation that made a great deal of news but came to nothing.

His successor's White House staff director, Hamilton Jordan, became a special prosecutor's "target" in 1980 because of someone's allegations that Jordan had sniffed cocaine in the men's room of a New York cabaret. Again, it came to nothing except bulging scrapbooks for Jordan.

The same thing has happened in this administration -- a long and fruitless Senate committee investigation of Labor Secretary Raymond Donovan for alleged "Mafia ties," followed by two investigations by a special prosecutor who concluded his labors with an empty hand.

When these things run their course, newspapers move on to new intrigues and interests, leaving behind all those scrapbooks. Some people think that is unfair. One of them is Ronald Schiavoni, a New Jersey construction contractor with an Italian name, a former business partner of Raymond Donovan.

Schiavoni, contemplating his own newspaper clippings, wonders if the American press really has mended its ways since McCarthy passed to whatever reward awaited him. He suggests that we have simply acquired new targets and new code words: For "Communist" substitute "Mafia" and the circle is closed.

To be "linked to a reputed Mafia figure" today is not unlike being "linked to an alleged communist" in the 1950s. Anonymous allegations are broadcast. Raw FBI files enter the public domain. Grand jury materials mysteriously find their way into unauthorized hands. And all that, in Schiavone's view, becomes the stuff of investigations and of ongoing newspaper coverage -- just like the old days.

"This is where I found fault with the press," he says. "That the press will not now go back and say: 'Hey! We have to tell you readers that there was a source or several sources who were feeding us information that we had no reason to believe was untrue. It was in the interest of the public to know about the background of a cabinet appointee. But a lot of people were injured by it and we want you to know that these sources had an ax to grind or did it for reasons still mysterious to us. (Some of those sources have since been indicted for perjury.) This is the failure of the press. . . . Our reputations are damaged and our children will probably have to live with it for the next 25 years. . . . I daresay there's probably nothing that could be done about it. But suppose somebody else comes down the pike? Will the press indulge themselves again?"

Probably. We follow fresh spoor wherever it leads, leaving our own litter on the trail. Our motives are ordinarily high-minded, our methods are ordinarily lawful and our successes ordinarily transcend our failures. Will we ever get it all right? No. But Schiavoni has a point. If now and again we retrace some of the barren roads we have followed, we probably will profit from it and leave fewer wounded in the ditch.