THAT WAS GOOD television and bad history when David Frost and Richard Nixon grappled for 90 minutes on Channel 5 Wednesday night. Mr. Nixon has revised his interpretation of the Watergate events that caused him to leave office in August of 1974. He no longer explains his own errant actions as the behavior of a President seeking to limit the "national-security" damage tot he nation and one who was abysmally ignorant of what had been going on.

His emphasis now is on what he describes as an early attempt to limit the political damage of Watergate and on his own large-heartedness as a kind of tragic flaw. He could not help trying to act as a defense lawyer for Bob Haldeman and John Ehrlichman, he said. He had let his heart get the better of his head. He just did not have the instincts of a "butcher."

In a way this line of defense is more tawdry than what has gone before. It puts it all on Mr. Nixon's friends and associates whom he was allegedly trying to help, and it implies that had it not been for this excess of human decency Richard Nixon would not now be the lonely exile of San Clemente. That, of course, is exactly wrong. Mr. Nixon's efforts to save himself were what got him in trouble. His closest aides had been acting in his name and with his authority, presumably carrying out what they took to be his purposes. He tried to conceal his own involvement as well as theirs. He told a lot of lies. He finally got thrown out of office. That is what happened.

We do not mean to be too cut-and-dried about it. There were some very emotional moments in Wednesday night's interview - Mr. Nixon's account of the strain of firing Messrs. Haldeman and Ehrlichman and his recollection of his last evening in the White House, accompanied by the concession that he had "let the American people down." But these were pitiful moments, not ennobling ones. And perhaps the most piticul moment of all was that in which the former President asserted that he would not "grovel," which he seemed to equate with admitting that he had knowingly done wrong. But Mr. Nixon has laready "grovelled" in this sense - although he doesn't seem to recognize the fact - in accepting the pardon offered by Gerald Ford.

What the former President evidently does not understand is what people are asking of him now. As we perceive it, what is being asked is ome acknowledgment on Mr. Nixon's part that he in fact understands what happened to him - and not incidentally to the country - in the two-year Watergate drama. This he either will not or cannot give. He still sess twisting swords and fifth columns and partisan excesses as the engines of his downfall. And this is so, even though Mr. Nixon now says he has only himself to blame - because what he is blaming is some extravagance of compassion he purportedly felt for the sinners around him.

We don't for a moment suppose that the impulses of all those demanding more from Richard Nixon are pure or that there isn't a large dose of sanctimony and even sadism on the part of some who keep insisting that he must "confess." But we do not think that most people who are unsatisfied with the Nixon post-presidential performance so far are asking something reasonable: evidence that Richard Nixon will accept the moral responsibility for his actions, not just the political responsibility. This, as he made plain Wednesday night, he is still unwilling to do.