A lot of Americans seem suddenly disappointed to find that Nelson Mandela, the man they welcomed to this country as if he were a reincarnated Mohandas Gandhi or Martin Luther King, is neither one.

The black South African anti-apartheid leader may be just as brave, eloquent and charismatic as they were, but he is less willing, it turns out, to confine his weaponry to turning the other cheek.

President Bush and a chorus of voices as diverse as American Jewish leaders, Dr. King`s colleagues, Cuban Americans and members of Congress have called on Nelson Mandela to emulate Martin Luther King more closely. By this they mean he should renounce violence, embrace civil disobedience and distance himself from some of his old comrades-in-arms, such as Communists and the notorious human-rights violators Yasser Arafat, Moammar Gadhafi and Fidel Castro.

But South Africa, as Nelson Mandela responds gently but firmly, is not the American South of the 1960s. He has a good point. When one considers the horrendous level of violence and degradation the South African government has inflicted upon its black population over the decades, it seems ludicrous to rebuke Nelson Mandela for his refusal to rule out the use of force in securing basic rights for his people.

And considering the sluggishness with which the United States and other major nations came around to his side by imposing sanctions against the South African government, it`s understandable that the African National Congress, which Nelson Mandela leads, feels some loyalty to its early allies, even if they happen to be Communists or Arafat, Gadhafi and Castro.

''Non-violence is a good policy when conditions permit,'' Mandela explained to an Atlanta airport gathering where local civil rights leaders suggested he should convert to Dr. King`s philosophy of non-violence.

It`s convenient to put world figures into clearly defined slots of good and evil. But the real world is not that tidy. We fall back on absolutes with the most difficult issues, too: Are you for legal abortion or against it, for the environment or against it, for the right to die or against it? Try to appreciate the shadings in between the absolutes, and you are thrashed by both sides. Nelson Mandela`s demeanor is gentle, benevolent; but he is also a man brutalized by decades in prison and decades of suffering from the

brutalization and subjugation of his people in their own country. And now he should emerge from 27 years in prison and transform himself into America`s romantic ideal of a saintly hero-celebrity? Not likely.

By making peaceful protest almost impossible, to borrow a phrase from Dr. King, the South African government made violent protest virtually inevitable. That was the grim conclusion the African National Congress reached almost 30 years ago after nearly a half-century of bloody state-sponsored repression.

Today, under F.W. de Klerk, conditions in South Africa may finally permit the ANC to embrace non-violence again. But blacks and whites have only begun long-awaited ''talks about talks.'' It is too soon after Nelson Mandela`s release from prison and too soon in the process to dismantle apartheid and set up a new power-sharing arrangement to expect black leaders to surrender their repertoire of tactics, their calls for sanctions or their alliances with controversial friends.

In time, Nelson Mandela and other black leaders must offer assurances that a new South Africa will do more than duplicate in black hands the abuses perpetrated by white hands. South Africa`s government seems bent on reform, but no one expects apartheid to disappear overnight. Neither should anyone expect Nelson Mandela to change his strategy overnight.