Maximum cruelty has always been the directive behind ICE (Immigration Customs and Enforcement), the monstrous federal apparatus created in 2003 to terrorize undocumented communities under the pretense of protecting the public. Throughout its six hour-long episodes, Netflix’s documentary series “Immigration Nation,” from Shaul Schwarz (“Narco Cultura”) and Christina Clusiau (“Trophy”), provides access into the inner workings of the infamous agency while juxtaposing a myriad of perspectives on the issue.