Well, if a Korean car factory worker live and work illegally in the country, then it makes total sense to remove them, regardless if they are serial killers or not. A company shouldn't even hire anyone who is not eligible to work legally in the country. There are laws that need to be followed like everything else.

It sounds like you're saying that you want the country to have open borders so that everyone can come live and work here given they pass some basic checks (no criminal history for example). I am not saying that is wrong, but that's not how pretty much every country in the world operates.