The two letters are very similar. Both refer to "a friend and I" who attended a show given by a group popular with young people. Both refer to souvenir T-shirts on sale outside the auditorium. Both state the price of the T-shirts as $8.

One letter says the writer proferred a $10 bill and his friend gave the vendor a $20 bill. The other says both handed over $20 bills.

Then both letters say "two men in plain clothes" arrived on the scene. The newcomers said they were detectives and they were arresting the vendor for selling stolen T-shirts. Thereupon they hustled him off into the crowd, and of course the buyers got no T-shirts -- and, alas, no return of the money they had handed over.

I can find no record of official arrests at the time and place stated. So it appears to me that the four who were victimized were probably duped by a very old scam. A variation of it was a key ingredient in the plot of lthe movie "The Sting," in which phony policemen also show up at just the right moment.

Every adult can probably recall at least one episode in his life in which he was fooled by something that appeared to be a legitimate transaction but later took an unexpected turn.

It saddens me, therefore, that so many who criticize The Washington Post for running the Janet Cooke story about "Jimmy" refuse to accept the explanation that Post editors believed their reporter.

The editors' trust may have been misplaced and naive. The editors may have been derelict in not insisting on being told in confidence the names and addresses of the boy and his mother. Perhaps they should have been more hard-nosed with a reporter who said her life might be in jeopardy if she revealed names and addresses. I will concede all of these points.

But as one who has himself been duped on many occasions, I am in no position to criticize a fellow patsy. I will have to leave that to those with perfect judgment who have never been fooled by a skillfully crafted scam. Let him who is without gullibility cast the first stone. And if there is need for cirticism, surely it can be stated in a responsible manner rather than with gleeful vindictiveness.

The Janet Cooke incident in no way detracts from the good investigative reporting done by The Post, The New York Times and other publications that helped expose the conduct of Richard Nixon and Spiro Agnew. Neither man resigned because lies tarnished his reputation. They were brought down by truth, not fabrication.

We all make mistakes and must pay the penalty for them, but there is no need to savage a hapless victim of poor judgment.