THE FRIENDS of Paul Thayer think it would be a shame if the former deputy defense secretary had to go to jail for obstruction of justice, a charge to which he has pleaded guilty. Mr. Thayer is a man of considerable public and personal accomplishment. But the stature and responsibility to which he has risen make him, in our view, more rather than less culpable for his serious offenses.

Mr. Thayer's friends are not just anybody. Those who have written letters on his behalf to the federal judge who will sentence him include a former president of the United States, current and former chairmen of the joint chiefs of staff, the chairman of the Senate Armed Services Committee and a galaxy of corporate lawyers, defense industry executives and holders of other high office. They testify not only to his professional achievements, but also to his personal acts of charity, including helping a young high school dropout to build a successful career and playing a major role in raising money for the Vietnam Veterans Memorial.

But Mr. Thayer is not accused of a peccadillo. He has pleaded guilty to obstruction of justice and giving false testimony in connection with a scheme that netted $2 million in illegal stock profits for his longtime girlfriend, Sandra Ryno, a Dallas stockbroker, Billy Bob Harris and six others. Mr. Thayer, a multimillionaire, did not pocket any of the proceeds, but he clearly valued his relationship with Sandra Ryno who, according to his lawyer, had become "increasingly reluctant to take large gifts of cash."

There is no ambiguity about the illegality of Mr. Thayer's activities. The deals, as described by the prosecutors, included such colorful details as the use of go-betweens, pay phones and borrowed credit cards and the delivery of the payoff in a bread basket -- and the prolonged attempts to hide them from SEC investigators included perjury and other obstructions of justice.

Insider trading is not a victimless crime. Some potential victims are easily identified -- for example, the stockholders of Anheuser-Busch, which is suing Mr. Thayer and his co-defendants for more than $250 million that, it alleges, his insider trading cost the company by driving up the stock price of a firm it was then acquiring. Less obvious, but no less real, are the loss of confidence among small investors who increasingly believe -- not without reason -- that insiders are taking all the best gains and walking away from the serious losses, and the encouragement of speculation in a market in which long-term returns are already undervalued.

As methods become increasingly sophisticated, punishment of those who are caught is the only hope for curbing insider trading. That means cracking down on everybody who gets caught -- not just thoithout an adequate list of friends. As a sophisticated investor, Mr. Thayer surely understood the costs and consequences of his actions. What justice would there be in sentencing him to a lesser penalty than if he had been the poor, uneducated perpetrator of a commonplace theft?