Martin Luther King Jr. during a television appearance in 1957. AP Nearly 50 years ago, the FBI sent civil Martin Luther King, Jr. a letter threatening to make public sordid details of his sex life if the civil rights icon failed to do the "one thing left for you to do."

That one thing, King believed, was to commit suicide. Obviously he didn't heed the warning, and even after King's affairs were revealed he continued to be remembered for his civil rights legacy.