That is, he regrets the intrusion of moral questions into professional matters best conducted by wise men like himself; regrets, in other words, that human beings everywhere consider him to have conducted himself barbarously in prosecuting the Vietnam war with reckless disregard for human life and health.
According to HuffPost, Kissinger said in Washington this week that
he regretted that what should have been straightforward disagreements over the U.S. approach to Vietnam became transmuted into a moral issue - first about the moral adequacy of American foreign policy altogether and then into the moral adequacy of America."
Next, I suppose that Kissinger "regretted" that irritating way in which the sun keeps rising in the east.
The HuffPost reporter scrambles over Kissinger's typical evasion. Consistently, tenaciously, for forty years, Kissinger has insisted that it would be unseemly to judge his policies--policies that cost the lives of (at least) hundreds of thousands of people in Southeast Asia--as morally debased. And he has done so without losing his wise man status in the eyes of official Washington.