Guardian: The rhetoric of Martin Luther King's "I have a dream" speech remains electrifying, as tributes this week to the poetic genius of those words spoken half a century ago have reminded us. But how should we gauge its legacy? The march by 250,000 people on Washington DC that day in 1963 wasn't for freedom alone, it was also for jobs. Then, two in every five black families in the US lived below the poverty line. Today, a quarter still do. For all the explosion of wealth since King's death, millions of...