In the privacy of his taped-recorded office, Richard Nixon called George Shultz a "candy ass" when (as secretary of the treasury) Shultz refused to give Nixon's men access to the tax returns of the former president's "enemies." Considering the source and the circumstances, that's the next best thing to a Medal of Freedom.

Now, Shultz as secretary of state has again taken a stand on principle and his president's men are again doing him the same sort of backhanded honors. They are bushwhacking Shultz with anonymous slurs on his loyalty and fitness for office: Shultz refused to submit to Reagan's efforts to unmask spies by administering polygraph (lie detector) tests to the men and women he has entrusted with the highest offices in his command.

Do not be put off the point of principle by the president's scaling back of the original directive or his slap-happy suggestion that he would exclude himself as well as Shultz. An administration's character is better judged by its initial inclinations than by its knuckling under to public pressure. The point of principle has to do with old-fashioned values such as honor, dignity and integrity. And the implications run far beyond the potential of ruining reputations and careers by putting them at the risk of a notoriously unreliable piece of machinery.

What the president would have, if he could, is a sweeping expansion of a practice earlier administrations routinely employed for strictly limited purposes to control the security of a narrow range of sensitive intelligence operations.

Even the president's efforts to meet most of Shultz's objections (polygraph examinations will now be confined to use "in conjunction with other investigations and security procedures in espionage cases") are scarcely reassuring unless you know what is meant by "espionage." The espionage laws, dating back to 1917, are loose enough to have alring with some of his work. Margaret Thatcher or that of French President Francois Mitterrand, as reliable allies, if they started wiring their Cabinet ministers to lie detectors to see if they were behaving treacherously? And what would they think of a leader of the free world who did so?

We should be cheered in this holiday season that there is at least one voice in the Reagan administration to remind us who we are and what we stand for.