A slight sliver of a silver lining

I can understand, although I regret, the rhetoric of President Reagan's verbal attack on the Soviets over the Korean plane affair. He made it sound worse than the Japanese attack on Pearl Harbor which it was not, no matter how brutal and unjustified.

He was under pressure from his extreme right constituents to take drastic measures, including breaking off diplomatic relations and cutting off all trade, including the just completed grain contract.

Since he was not going to take the strong action they wanted he obviously felt impelled to try to make it up to them by flaming words. He had to reassure them that he is still a true believing anticommunist.

Well, he has done that, at the price of undercutting the effect of the Soviet deed of violence on the rest of the world.

It was a wicked deed. Anyone can see that it was, and that it shows the Soviets to be capable of a degree of brutality which is out of date in today's world. The mere deed, all by itself, and without embellishment from Washington, undercuts the ''peace movement.''

By this deed the Soviets damaged all those people and political forces who were resisting the deployment of new American weapons in Western Europe. One missile fired at that unhappy plane wiped out months of patient Soviet ''peace'' propaganda. The Soviet bear ceased to be plausible in its ''peace-loving'' garments.

But this happened automatically without instruction or underlining from Washington. The effect was weakened when Mr. Reagan came into the act because it made the affair seem to be more an episode in Mr. Reagan's personal feud with the Soviets rather than an affront to all civilization.

The Canadians understood this when they banned Soviet Aeroflot flights to Canada before Mr. Reagan spoke his piece. They did it on their own because they felt both aggrieved and angry, not because Mr. Reagan pushed them into it. It rang as genuine because they did it first. Similar actions by others coming after the Reagan speech will seem less genuine, more the act of clients falling in behind an American lead.

There was no need to lead here. The actions of others would carry more weight at the Kremlin if done as the Canadians did. The men in the Kremlin will just shrug off a collective action orchestrated by Washington.

But there remains out of the tragedy one slender basis for some hope for those who would like to see this become a less dangerous world.

In the history of the East-West relationship since World War II we may be nearing what has been called the ''second cold war.'' The first cold war dated from 1948 to President Nixon's trip to Peking, and then to Moscow in 1972. It was followed by ''detente'' which flourished briefly but gradually wilted even before it was fatally damaged by the Soviet invasion of Afghanistan, the suppression of Solidarity in Poland, and the steady increase in Soviet military power.

There was a fourth factor. American opinion in general (with many individual exceptions) saw detente through rose-tinted glasses. Much was expected of it beyond what it could provide. Its strength lay in a mutual recognition that war between the nuclear superpowers would in effect destroy both. They sought machinery which would reduce the danger of such a war.

Its weakness lay in the assumption by many in the West that the Soviet Union would become a contented power, would cease trying to expand its range of influence, would cease trying to outbuild the US in weapons.

The invasion of Afghanistan and the reimprisonment of Poland brought a shock of disillusionment in the West. The millenium had obviously not arrived. The Soviet Union was still an expansionist power and would still seek to outreach the US in weaponry if it could. Detente has become a bad word since the invasion of Afghanistan.

But the need for agreed limits on the methods to be used in the continuing competition between the US and the USSR remains as great as ever. The Korean plane tragedy is a reminder that the Soviets think of the world as being in a state of competition and that they will pursue their competitive role with brutality when they think it will serve their purpose.

There is in the air a recognition on both sides that it would be prudent to salvage those elements of detente which were designed to reduce the danger of nuclear war. But thanks to the Korean plane tragedy there will be less inclination to illusions in the West. If there is to be a second detente, it will be more restrained and realistic than the first, and hence might last longer.