" that contained brothels and opium dens."

Oh god, talk about better times.

Legal immigrants = educated individuals with skills or individuals seeking an education and skills.

Illegal immigrants = uneducated individuals who do not try to assimilate to the local culture and use the country they come to and try to replicate the same regressive behavior that made the countries they came from so terrible.

That's called intelligence at work - definitely on the higher IQ spectrum of the bunny scale.