Random trivia: he started life as Michael Luther King, Jr., but later changed his first name to Martin. So says the biography of him on the Nobel prize website. He also "traveled over six million miles and spoke over twenty-five hundred times" between 1957 and 1968. In addition, he was "arrested upwards of twenty times and assaulted at least four times". An article on CNN notes that "[a]t the time of his death, King was working on anti-poverty and anti-war issues. He had spoken out against the Vietnam War in 1967, and was in Memphis in April 1968 in support of striking sanitation workers." I imagine at the time he seemed like the most dangerous individual on the planet to those in power.
Dangerous isn't the word; he terrified those in power. And sadly, we've not seen a leader of that magnitude since--at least not in such a public light. Everyone knows you can't fight poverty and war--how else will you spread the greatness that is democracy?