On a more rational level, executing the commander of Auschwitz does nothing but provide short-term satisfaction, but treating even the monster to a humane stand

On a more rational level, executing the commander of Auschwitz does nothing but provide short-term satisfaction, but treating even the monster to a humane standard affirms the values of democracy and sets an example for future generations. Think of how the American prison scandals of Guantanamo and Abu Ghraib affected the global perception of American justice. It was just a massive loss of international goodwill and credibility accumulated over a century. All the torture and kidnappings delivered very little practical return in the end.