After WWII, American soldiers forced German soldiers and citizens to look at photographs and video of massacred prisoners in concentration camps. In addition, many were also forced to handle the bodies of the victims (e.g. transport, bury). This is technically a war crime because it falls under “collective punishment,” but the result is that Germany is deeply ashamed of their past, nominally

this is a deeply unscientific approach as it ignores the many other factors in play. For evidence of such a conclusion you would need a study of the effects of exposure to violent images on people convicted of serious violent crime

I would personally argue that the efforts of the soviets in East Germany and even the occupation of west germany were largely responsible for the public shame