I have been out of the country twice this year. The first time, I was in Mexico when protests broke out in Ferguson, Missouri, over the shooting death of Michael Brown; more recently, my two weeks in Argentina coincided with nationwide demonstrations against the lack of grand jury indictments in the cases of Brown and Eric Garner, the Staten Island police chokehold victim. Witnessing a nascent anti-police brutality movement from a distance has given me a different perspective on it, because the novelty of getting out in the streets in America and demanding justice stands in stark contrast to the...