Sci-fi blockbuster District 9 “explores the plight of huge, chitinous aliens who’ve been trapped and maltreated for decades after their unexpected appearance in the skies above Johannesburg — touching on themes of apartheid, xenophobia and redemption along the way. Now District 9 is playing in South Africa … and many of those emerging from theaters over the weekend responded to subtleties in the film that may have been lost on many American audiences.”