In 1982, President Reagan named to the U.S. Commission on Civil Rights a Philadelphia radio evangelist with no credentials for the job, the Rev. B. Sam Hart. Mr. Hart quickly became an embarrassment to the administration, and his nomination was withdrawn.

The next year the president switched strategies. Moving to take control of the commission, until then a thorn in his side, he offered three nominees with impeccable credentials who agreed with his positions on such issues as busing and affirmative action. The three, all Democrats, were Morris Abram, a longtime civil rights lawyer and former president of Brandeis University; Robert Destro, a law professor at Catholic University here, and John Bunzel, research fellow at the Hoover Institution and former president of San Jose State University.

The seriousness of these appointees helped to disarm the president's critics and gave new weight to his positions. Now that same gravity has come round to nip the administration itself in the rear.

Mr. Bunzel has written a letter to the chairman of the commission, Clarence Pendleton, urging him to resign. Mr. Pendleton, also a Reagan appointee, had been a relatively reserved figure before the 1984 election. Once the election was over, he shifted into a different gear, becoming more combative. Among other things, he began attacking the leaders of established civil rights organizations, calling them "media-designated black leaders," "the new racists," "immoral" and "part of a race industry and . . . a problem for black progress."

Their response was to break off completely an already reedy relationship with the commission and call the chairman a "lackey." Mr. Bunzel's belated response has also been to denounce him for cheapening the debate and costing the commission the very credibility that -- although Mr. Bunzel did not say so -- the appointments of 1983 helped to provide.

The letter is extraordinary in its directness. It says that Mr. Pendleton has "stifled, rather than contributed to, the kind of rational and respectful debate of complex issues that is much needed today."

"By attacking the motives and integrity of your opponents," it continues, "you have lost whatever opportunity you may have had to exert effective influence on the work in which we are all engaged. These men and women, and the organizations they have led, have played a major role in bringing about the legal and peaceful transformation of American life. They have a record of which they can be proud. While I often disagree with their approaches to affirmative action and other issues, I submit that they are not deserving of your contempt or derision."

Well said. Mr. Pendleton says he won't resign, but Mr. Bunzel is right: it would help if he did.