AN EMINENT OFFICIAL of the regime in Vietnam, Dr. Ton That Tung, has been making the rounds in Washington Putting the case for American aid. It is regrettable but necessary to say that he is doing so on spurious grounds. Dr. Tung, a cancer specialist who in his country's director of science and health, is appealing to Americans on the Basis of their presumed guilt. If you are troubled by the flow of "boat people," he says, you should understand they are being driven out mostly by economic hardship. "If you will help us economically, we will stop it. Our economy was destroyed by the war. You fought the war."

We have two objections, the first factual. It simply is not the case that economic hardship resulting from the American role in the war is forcing the exodus. What is happening is that North Vietnam, having won, is exercising the victor's privilege and is remaking the South Vietnamese economy in its own socialist image. In the process, it is squeezing out many of the people who performed middleman functions, many of these ethnic Chinese. No one can doubt that the war did great damage to the economy, but that is not the main reason for the refugees. Hanoi's own political decisions are responsible, and foreigners are not required to subsidize them.

The second objection goes to the question of whether guilt is or should be a basis for making foreign policy. One can think of circumstances where it mattered: in the establishment of Israel, for instance. But Americans are by no means of the same strong and passionate mind about Vietnam. It is not merely that the war was, and remains, controversial to a degree not substantially eased by Hanoi's decision last year to stop demanding "reparations," the payment of which would have been an open acknowledgement of guilt. It is that Vietnam has altered the political-emotional equation by acts of its own since the war: by its treatment of the groups generating the refugees, by its aggression against neighboring Cambodia and by its willingness to lend itself to a Soviet global strategy. This is what has kept the Carter administration, which started out, after all, favorably inclined to Hanoi, from following through.

In brief, Hanoi blew it. This administration was more than ready to resume diplomatic relations and to consider aid, though not "reparations." First Hanoi pressed its demands to excess and then it made a series of decisions that cut the ground out from under its American constituency. For better or worse, American diplomacy toward Vietnam now can only be guilt-free.