Also, the idea that people from a crappy neighborhood wouldn't prefer to live in a much better neighborhood, is unrealistic. Europe is already much better because of the climate and vegetation and public infrastructure.

If you let them come here, they will continue to come, so long as their home country isn't better. 

 They’re benefitting by increasing their powers as people coming in believe a somewhat functioning democratic government is better than what they have at home. 

 They are right, it is better.