[kyashan]

Migration is not a problem per se. the real problem are its proportions, more specifically mass migrations. if someone wants to spend some time in a foreign country, that's fine (I'd like to do it myself). People don't immigrate spontaneously in large numbers, just those ones who have the skills and the will to integrate themselves in another country choose this option.
the real problem is when people are forced to leave en mass their own country because of starvation, political and social issues etc.
the same thing goes for internal migration.