That's the question, isn't it? Why not just do that? Who are you trying to keep out of the country, and for what end, and is that end best attained by removing people from the country who aren't the ones you are trying to keep out?
For instance, if you believe the border should be strict to keep out serial killers, what does that have to do with removing Korean car factory workers who aren't serial killers?
For instance, if you believe the border should be strict to keep out serial killers, what does that have to do with removing Korean car factory workers who aren't serial killers?