USA TODAY The claim: As FBI director, J. Edgar Hoover said 'negro unity' was the greatest threat to the U.S. In the days leading up to Juneteenth, which celebrates Union troops announcing the emancipation of slaves in Texas, a claim regarding longtime FBI Director J. Edgar Hoover's comments about Black people resurfaced on social media. Hoover was the director of the FBI for almost 50 years, from 1924 until his death in 1972. The social media claim focuses on his threat assessment of activist groups during the 1960s. "When FBI Director J. Edgar Hoover was asked what was the single greatest threat to the USA, he answered 'Negro unity.' Take a moment to let that sink in," says the text of a June 16 Facebook post.