Anyone who is African or African-American will tell you that they have trouble taking taxis in South Korea, that people refuse to sit next to them when using public transportation and that some stores refuse to sell them anything. Other complaints include Koreans refusing to speak English to them even when they do, or Koreans telling them outright that they dislike "black" people.
Where does this originate from? I will argue that there are two origins.
The first one is an older version, when in the 19th century European scientists attempted to define "black" people as the "inferior race". Let me explain. It was argued that the human being evolved in Africa, thus starting off as black, then moved to Asia, thus becoming Asian, then to Europe, thus evolving to its final, most perfect state-white. Therefore scientists argued that fetuses started off as Black, evolved as Asian and then came out as white. Fetuses that came out black meant that they did not evolve properly, and those who came out Asian only evolved partially. Dr. Down, who discovered the Down syndrome was himself a supporter of this theory and coined the term "Mongolian" to describe his patients who had the down syndrome because he argued that they had stopped evolving at the "Asian" phase. Of course this theory has been completely discredited since World War II.
This means that for a number of years, many people in the world did believe that black people were primitive men who had failed to evolve as "perfect" men. Though few Koreans would directly prove this theory right, you will often hear Koreans say that "Black people are primitive", that they "still marry several wives" and that they "refuse to dress up as westerners" and are not "suitable for an industrialized economy".
Let me stop here for a second. As a linguist, I should argue that one of the first theories to demonstrate scientifically that all men regardless of color or ethnicity were equal was a linguistics theory: Noam Chomsky's Universal Grammar. Chomsky argued that all men had a "grammar component" in their brain that made them acquire any language they were exposed to, and that therefore you could be from a hunter-gatherer tribe in Africa, then be adopted by a family in Cambridge, Massachusetts, grow up in a White middle class environment, speak just like people surrounding you speak, and why not end up attending Harvard or the MIT.
The second theory is a socio-economic theory which encourages racism towards black people in Korea. Koreans are convinced that most countries with majority black popualations are poor countries, and that African-Americans and black minorities around the world tend to be economically deprived. This fact tends to confirm their first intuition according to which black people are inherently inferior. But let's stop here again. Bermuda, a British territory but which is partly independent, is mainly populated by black people. It is by far the richest territory in the world. Its per capita GDP is 91,000 US dollars. It is a territory where you will see black people working as CEOs, chairmen, doctors, lawyers and any fine profession you can think of. The Bahamas, another country with a majority of black people, also ranks higher than South Korea in per capita GDP.
Fear of black people and racism towards black people has the same roots in Korea as it does in other industrialized countries where black people are minorities. Racism has been somewhat appeased through black role models in some countries (African-American singers and actors in the United States, soccer players in the UK and Turkey, tennis players in France) and while Hines Ward's popularity did change Korean people's views on biracial children, it certainly did little to change Korean people's views on Africans and African-Americans.