This was first written about by Diogenes Laertis around 300 A.D. in his book "The Lives and Opinions of Eminent Philosophers". In it he attributed the saying to CHILON of Sparta, one of the seven 6th Century BC philosophers and statesmen revered for their wisdom. So it's been around a very long time.
Which would mean we could not speak truthfully of Hitler or others who did evil things.