The logic of genocide 
do unto others as has been done unto you.
 
Hitler (Mein Kampf,1924): “If at the beginning of the War and during the War twelve or fifteen thousand of these Hebrew corrupters of the people had been held under poison gas, as happened to hundreds of thousands of our very best German workers in the field, the sacrifice of millions at the front would not have been in vain.”

As German soldiers had died as the result of poison gas in the First World War, so Jews would be required to die from poison gas in the gas chambers.

Jews in the gas chambers symbolized German soldiers in the trenches--suffocation by poison gas.

Identification with the aggressor: do unto other as has been done unto you. Hitler Identified with British leaders who had inflicted Germans with attack by poison gas: do unto other as has been done unto you.

The logic of genocide follows from the logic of warfare. If Nations have the right to kill enemy soldiers by using poison gas, why would Hitler not also have the right to kill Jews--Germany's mortal enemy--through the use of poison gas? The logic of genocide followed the logic of the First World War: kill your enemy through the use of poison gas. Do unto others as has been done unto you.