That Koreans discriminate against foreigners shouldn't be any surprise. 1) what people can you think of that didn't take a hell of a long time, in constant contact with different looking/speaking/believing/etc foreigners, to cozy up to them? The only people that come to mind are some of the Native American tribes that welcomed the European settlers with open arms - and look what happened to them, eh?
2) And look at Korea's relatively short history of contact with foreigners - first, the French send some Jesuits to teach some idiotic religion called Christianity; they get executed, just as (the Koreans thought) a bunch of Koreans trying to spread Korean ideas uninvited in France would; then the French send a shitload of soldiers to exact revenge - you know, rape, pillage, murder, etc. (Anyway, the French soldiers got killed, so France decided to go rape, pillage and colonize an easier target, Vietnam as it turned out.) The Koreans decide, Jesus, got to stay away from these pale-faced pointy-nosed barbarians, and shut themselves off from the outside world. Until Japan shows up to save the rest of Asia from European colonialism - by colonizing it first.
After the Yankees kick the Japs out, then the Koreans get 50+ years of multi-racial United Statesian troops living in their backyards, regularly committing rapes and murders against Koreans and then getting whisked out of the country to an United Statesian court for a heavy... slap on the wrist. Fuck, in the U.S., if a Mexican accidentally kills a white girl half the country will be calling for all tanned-skinned people to be shipped off to Abu Dhabi. 3) Besides, it is not as if the U.S. is home to any kind of ideal state of non-racism. It may seem like it from within light skin, but talk to someone whose ancestors are not from Europe - try a Mexican or Arab, for starters - and ask them what the U.S. is like to live in. 4) Guess where the Koreans got the idea that black-skinned foreigners are the worst of the lot, given that Korea and Africa never seemed to have much historical interaction... I'd wager it's the light-skinned foreigners.
Which brings me to: 5) an United Statesian lambasting another society for its racism is like a serial rapist criticizing a pornographer for disrespecting women.
Yeah, South Korea sucks for being hellish for women and racist to foreigners (esp. if you are a South Asian migrant worker), but you know what? At least it doesn't go around the world bombing women and kids, supporting brutal tyrants against their own populations, and forcing economic policies that amount to mass murder down the collective throats of poor countries.
[/End Devil's advocacy]