''Polite society'' is an outmoded phrase but we need to use it to get into perspective the brutal action taken by Soviet military authorities against the South Korean airliner which strayed into Soviet air space.
Under international law and conduct it is legal for the Soviets, or for anyone else, to forbid unauthorized traffic through their air space, particularly over military areas. It is also legal to take whatever measures are deemed necessary to protect that air space from unauthorized use.
Others have done in kind although not in degree what the Soviets did last week just south of the island of Sakhalin, which is loaded with Soviet air and sea bases.
Bulgaria shot down an Israeli passenger plane in 1955. All 58 persons aboard were killed, including 12 Americans.
Israel shot down a Libyan passenger plane in 1973. There were 113 persons aboard of whom 5 were French, the others Libyans and Egyptians. There were 7 survivors.
This is not the first time the Soviets have shot at a plane which they alleged to be intruding in their air space.
They forced down a South Korean airliner in 1978.
This matter differs from previous matters of a like kind in that the plane carried 269 persons of whom over 50 were Americans. There were also Koreans, Japanese, Australians, and Canadians.
Like the others, this was a scheduled international flight.
The Soviets intercepted and followed the plane for 2 1/2 hours before shooting it down.
Therefore their action was not a sudden reaction to something unexpected. It had to be a deliberate reaction after ample time for consideration and for taking other than violent means to protect their air space.
Hence we are dealing here not with something illegal or unprecedented, but with something which, to revert to a Victorian phrase, ''nice people don't do.''
There is a code of conduct among civilized countries. We do not shoot down each others' airlines when they stray by accident over each others' forbidden zones. There is an elaborate ritual for giving warning and for escorting a plane away, or down. The last thing any ''civilized'' country does is to shoot down a harmless commercial airliner loaded with unarmed passengers of various nationalities.
The phrase ''officer and gentleman'' survives from those Victorian codes of conduct which distinguish between members of ''polite society'' and outsiders we used to call barbarians.
What makes a person a ''gentleman''? There are two main features of ''gentlemanly conduct.'' The first is being considerate of the feelings and interests of others. The second is refraining from violence.
The above gives us the necessary clue to how the world will react toward the deed of Soviet brutality and violence.
''Polite society'' simply excludes from its social activities those persons who violate the code.
I would no more want at my dinner table a Soviet officer who had a hand in this deed of violence, or any Soviet citizen who tried to make excuses for it, than I would want a Nazi concentration camp guard or a member of an El Salvador ''death squad'' which still, we are told, goes out on its nightly round of killing.
The United States is going to continue to sell grain to the Soviet Union because, as President Reagan was quick to say, another grain embargo would hurt the American economy. It certainly would not make the Soviets less paranoid about their military frontiers. And the US is not going to pull away from exploring with Soviet diplomats the possibilities of new curbs on the arms race. A fair arms control agreement is as much desired in Washingon now as ever - if it can be had.
But a time of social ostracism is expectable and it just might cause the Soviets to be more restrained in the future. This was an unnecessary and uncivilized act of violence. It is the sort of thing ''nice people'' do not do. Civilized countries will let them know by behavior patterns that they have committed another deed which puts them beyond the pale of ''polite society.''