Korea has a highly hierarchy oriented culture. Everyone and everything is assessed according to the certain ratings and rankings (top 5, top 100, the more or less prestigious brand, fashion, utensil and so on). White Americans are thought of being superior, Japanese probably too, Vietnamese are inferior although above Indians or Philippinos. All that silently, of course. Par excellence, Koreans are the best, however - in reality they will have higher opinion of certain groups and almost openly disparaging attitudes toward another ethnic groups. All based on their “ratings”.
That's just how things are. However, Vietnamese (or anyone else) may go up in the popular charts — Koreans have no bias in this regard. Just need to be successful (and gain wide recognition, preferably by white Americans). Good luck.