The American ambassador in Moscow stayed away from Soviet celebrations of V-E day this week. It's a pity. In the larger scale of things, the reason cited for our coolness -- the Soviets' shooting of the American major in Berlin -- does not measure up to the loss of an occasion to show respect for the single, great (and unrevised), joint Soviet-American enterprise: the defeat of Hitler Germany. Sensible persons -- there are many sentimental persons -- cannot imagine that an American salute would change anything in the current equation. But some things should be done without thought of the return.

Consider the way it was for an American who was in Moscow 40 years ago on V-E Day. "As soon as the street crowds spotted the small U.S. flag on my car," Leo Gruliow recalled in an anniversary piece in the Christian Science Monitor, "they surrounded me, pulled me from the car and hauled me into the center of a cheering, laughing cluster. People fought to shake my hand, kiss me, embrace me. Never had I felt such a burst of warmth and friendship."

Surely it was a genuine burst, though it is hard to imagine that the Soviet dictator Joseph Stalin shared in it. "I hate Germans," he had confided to Eduard Benes in March; his eye was on reconstructing Europe so that "never again will attacks against Slavs be repeated." To Sen. Claude Pepper, he went on to say that the allies' anti- German tie "no longer exists, and we shall have to find a new basis for our relationship in the future. And that will not be easy."

On the streets of Moscow, however, the Soviet people were enjoying perhaps the single moment permitted them, before or since, to express unrelievedly friendly feelings toward the United States. Briefly, the clouds of distance, fear and Kremlin-induced hate had parted. There is no point in lamenting the passing of that time of mutual exhilaration. It was as gaudy and perishable as the fireworks that marked the day. Nonetheless, it left some troublesome myths behind.

In the United States, many people still feel cheated. They wonder how the spirit of wartime cooperation could have been lost, whether it could not have been sustained and applied carefully in small doses to subsequent events. And could not some part of the spirit of the Elbe, where American and Soviet soldiers met, yet be revived? Soviet propaganda has made diligent use of these doubts for decades, encouraging Americans to take all the blame for the lapse upon themselves.

Well, we Americans made mistakes, misunderstood some things badly. The American postwar purpose in Europe, nonetheless, was principled and remains beyond apology: to bring freedom and a new life. Where American power reached, this American purpose was generally well served. Over the years the revisionist arguments blaming America for the Cold War have, for me, worn increasingly thin.

A second myth is more difficult to speak of. For all of its terrible costs, World War II was actually a deliverance of sorts for the communists. The war gave the people an honest external enemy and let the regime take a positive patriotic role.

It is relevant here that Hitler killed perhaps only one-half or one-third or as little as one quarter the number of Soviet citizens whose deaths can be attributed to acts of Kremlin power. The accepted figure of casualties lost to Hitler is 20 million. Soviet estimates of people lost in the imposing and consolidating of communist rule, by purges, induced famines, expulsions, executions, abandonment and so on, run up to 80 million.

Ponder those figures and you begin to understand why to this day the regime encourages the people to lavish such tremendous outrage on the Germans. The system that inflicted these losses upon its own people is, of course, still in place. The member of it most associated with mass criminal brutalities, Stalin, was hailed by the new leader, Mikhail Gorbachev, at a Kremlin rally on Wednesday and given strong and sustained applause.

I have never found a satisfactory way to put together the two elements of Soviet participation in the war. There is the great valor of the Soviet people and their immense sacrifices in a cause in which the United States reaped major benefits but suffered only 5 percent of Soviet wartime losses. There is the cynicism of the communist leadership in putting the war to its own uses, inside and outside the Soviet Union.

Still, there is an abiding requirement for a civil dialogue with the one power with the capacity to inflict unbearable damage on the West and its friends. This is one of the two reasons why it would have been good for President Reagan to find a better way to pay American respects to the Soviet Union this week. The other reason is simply that valor deserves a tribute.