I visited the Embassy of South Africa this week, and as I approached the heavily secured embassy doors on Massachusetts Avenue NW, images of Negro-haters lurking at Billy Bob's Bar and Gun Shop swirled in my head.

Then I met Pieter Swanepoel, a white South African information counselor, and realized that this was more serious than anything the Confederacy had ever dreamed up.

Swanepoel was a preppy. "I'm real keen on cycling," he said with a friendly smile. He was 36, had a neatly trimmed beard, wore a gold watch, Cecil Rhodes-style trekking shoes and a light brown suit he says he bought at Syms. On his office wall hung a picture of white South African boxer Gerrie Coetzee defeating the black American heavyweight John Tate.

Sitting face to face with Swanepoel, I felt that he had mastered some ancient art of deception.

So I had to ask him if he felt strange talking to me, because I felt strange talking to him.

With disarming charm he said, "This happens in South Africa as well -- at the work place." But not at home, of course. Then, noting a wall rug of a Zulu warrior holding a spear and shield, Swanepoel said, "Some of my closet friends are of the Zulu tribe."

Swanepoel was a political science and economics major at the University of Pretoria and served at South African embassies in London and Australia before being assigned here three years ago. He had obviously learned his lines well.

Still, he refused to talk about specific South African policy. But it really was not necessary. The facts speak for themselves.

On Tuesday, Desmond Tutu, a black South African bishop and strident critic of South Africa's apartheid regime, won a Nobel Peace Prize for his efforts to effect change in that country.

Last week, Jesse Jackson led a demonstration and prayer vigil outside of the South African embassy to protest recent mass arrests and detention of religious and political leaders who have protested South Africa's racist policies.

And later this month, the South Africa Freedom Classic Tennis Tournament -- headed by Arthur Ashe -- will be held in New York to celebrate a cultural boycott of South Africa by athletes and performing artists in this country, and others around the world.

Swanepoel ponders the future with a smile while stroking an oversized model of a krugerrand -- the powerful South African gold coin.

"South Africa is changing," he said with a you-gotta-see-it-to-believe-it tone of voice. "There are coloreds and Asians in the government now," he said. "Debating the mixed-marriages act and the group areas act are high on their list of priorities."

Swanepoel cited the recently tightened Sullivan Principles, which is a voluntary code of conduct for U.S. corporations operating inside South Africa, as proof that the Reagan administration's policy of "constructive engagement" is working.

He has his views, to be sure, but is he blind to the living hell of blacks in South Africa? Swanepoel heads off the downside of "constructive engagement" with an off-the-cuff comparison. He recalls taking a tour of Washington -- including the poor and predominantly black Southeast section of the city.

"I can say that there are blacks in South Africa who live better than some of the blacks in Southeast Washington," he says. Then he hints that the differences in the ways of whites here and those in South Africa are really just a matter of style.

"I notice the economic separation of this city, where there is racial separation in South Africa." Swanepoel says. "I just find the practices fascinating."

Swanepoel says he will spend about another year in Washington, looking at these fascinating practices and, as a South African information officer, attempting to explain the worst of them.He does not look like the kind of guy who would do this kind of work. That makes his job all the more sinister.