Um, from taking walks a few blocks from my apartment and doing volunteering in such communities. Also just reading the local news. Also reading lots of ethnographies. Go read American Millstone (http://www.amazon.com/American-Millstone-Examination-Permane...) or Ghettoside and maybe you will rethink those scare quotes. I'm not sure how "void of civilization" is an unfair label for what is described in those books.

There were white (mostly Irish) inner city areas with a complete void of civilization, such as old southie, but those areas are less prevalent these days. That said there is lots of degeneracy among the white population in some areas too. I'd call those areas more of a partial void of civilization rather than an utter void of civilization.