I watched a living legacy to Dr. Martin Luther King Jr. on the anniversary of his birth Tuesday. Several hundred nonviolent demonstrators marched outside the South African embassy, protesting that country's policy of apartheid.

Unlike the protest marches that King led during the '50s and '60s, these demonstrations were against a foreign government's persecution of its citizens who happen to be nonwhite.

And the timing of this demonstration against the South African government was particularly appropriate because King himself had led so many mammoth nonviolent marches in his day and had spoken out so often against South African apartheid.

But the demonstrations outside the South African embassy are only a small part of King's legacy to nonviolent protest. It goes on all over the world and is reported on the front pages of newspapers every day.

In Argentina, hundreds of mothers wearing white scarfs marched in a circle in the Plaza de Mayor every Thursday afternoon for more than seven years protesting the deaths and disappearances of thousands of their children under military rule. They still march, despite the democratic regime there.

In Poland, a satellite of the Soviet Union, the Solidarity union utilized nonviolent techniques to gain new freedoms and rights for that nation's workers.

Of course King himself borrowed greatly from the legacy of Mahatma Gandhi, India's great political and spiritual leader, whose nonviolent actions led to India's independence from Great Britain.

And Gandhi was led by his ordeal with racism while practicing law in South Africa to read the works of an American writer, Henry David Thoreau, particularly his essay "Civil Disobedience." In that essay, Thoreau noted: "It is not desirable to cultivate a respect for the law, so much as for the right."

While the contributions of both these forerunners to his methods are clear, it was Martin Luther King who made nonviolent protest a respected, effective means to social change. It was King who combined the use of massive, peaceful marches and national television coverage to make the tactic familiar and universal.

In the decades since King used nonviolent tactics to tear down the walls of segregation and gain justice for American blacks, countless other groups in America have utilized nonviolent protest to redress their grievances.

Women, in their quest for equal rights; the aged and infirmed seeking to end job discrimination and secure entitlements; gays protesting discrimination based on sexual preference; and the handicapped all have used similar means to remove some of society's barriers against them.

Behind the psychology of nonviolence is a conscious effort to sway public opinion by dramatizing oppression. Holding up a mirror to an oppressor, nonviolent demonstrators seek to show him -- or in the case of South Africa, a nation -- his image as an oppressor. Of course there is one thing that the whole tactic of nonviolent protest assumes: that the oppressor, any oppressor, has a conscience and a capacity to wield power in a just manner.

Coming to grips with its image in the world community and wielding power justly are changes South Africa has resisted for years.

As far back as l960, when nonviolent demonstrators in Sharpeville, South Africa, protested apartheid, the South African government responded violently. Shooting 67 nonviolent demonstrators in the back, South African authorities perpetrated what came to be known as the Sharpeville Massacre.

And still, as late as last month, the killings continue in South Africa.

Crying out not only against the Sharpeville Massacre but against the system of apartheid itself in 1965, King called for an international boycott to combat apartheid.

". . . The time has come to utilize nonviolence fully through a massive international boycott which would involve the USSR, Great Britain, France, the U.S., Germany and Japan," he said at that time.

If King were alive today there is no doubt he would be outside the South African embassy on Massachusetts Avenue, protesting the actions of a nation that, as he put it, is reversing the human evolutionary process and "traveling backward in time from human to prehuman."