The president of the Louisville police union caused a backlash when he issued an open letter calling unspecified activists “sensationalists, liars and race-baiters.” Dave Mutchler is the president of the River City Fraternal Order of Police and a sergeant in the Louisville Metro Police Department. He distributed the two-page letter six days after a police officer shot and killed 35-year-old Deng Manyuon, a Sudanese refugee who attacked him with a flagpole. …