The myth of the Oriental Despot is part of a long, long intellectual tradition dating back at least to Ancient Greek Herodotus.

Rather than a myth it’s more like a stereotype I guess. In it, the West and East are diametrically opposed because the Greeks are a free people and the “Orientals” (just means easterners) are rules by despots. Later Europeans would claim this mantle as they considered rulers in the Middle East, India, East Asia and the America’s as “oriental despots” while they were free Westerners. This was used to justify imperialism and missionary work. Famously, the Chinese emperor’s prohibition of the opium trade was described as oriental despotism because it violated British rights to private property (the opium) and free trade (the drug trade). This was leveraged into a war on the emperor to make him accept the trade.

To get at your specific question, what the prosecutor meant was that the Nazi crimes were not only horrific, but they also exceeded what was expected of the West. To show how beyond the pale the Germans were, he compares them the mythic oriental despots.

People that invoke “oriental despots” rarely have a specific regime in mind, and so, any claim that follows is suspect to say the least. While the world east of Greece has certainly seen its share of homicidal maniac rulers, the Nazis really did set a new bar for horror.

Many current day historians argue that the violence of the 3rd Reich can best be compared to colonial violence and genocide. Moses Dirks is one prominent historian I’d recommend you read if you’re interested in the subject. Allie prosecutors in the Nuremberg trials were sensitive to this claim and avoided any arguments against the nazis that could apply to their empires. Nazis on trial often pointed out that they had not done anything that had not either been done to them or other people’s in the allied empires. Before he took power, Hitler famously said that Germany should model its conquest of Eastern Europe on the American conquest of the Navajo.

It was much easier and more comfortable to invoke the boogeyman of “oriental despots” rather than look at the colonial roots of the holocaust.