But the fundamental stupidity of Nazism discouraged even the most anti-Semitic of them (not all of them).
Brenus, I agree that it was stupid. However, if you look at it with the insane mind of Hitler, there was no alternative. First reason was that Hitler believed that Germany lost the war because of the uprise of the people caused by hunger. He realy thought that the unbeatable German army would have won, if the people at home would have go on supporting the war. So he believed that having enough food was one of the most important preconditions to win the war. Therefore, it was most important for him to get a lot of food from Ukraine, accepting the death of millions there.
Second reason was that he obviously did not attack the SU to free Ukraine. He wanted the land for Germany, or better said for Germans. The population there had to disappear, with only few working slaves. So he used the opportunity of the war to get as many of the Ukrainians killed as possible.
So you are right, the Germans could have done much better, but it was not a realistic option for Hitler.

The sanctions against Japan were the proximate cause of war with both Japan and Germany.
Kralizec, I agree that the sanctions should force Japan into war, as they did. But it was something else with Germany. Roosevelt did a lot of things to help GB and to provoke Germany: the lend & lease, the cash & carry, giving the Brits American destroyers, guiding convoys to the middle of the Atlantic, having long range air patrols over the Atlantic, occupying Island and Greenland and even attacking German submarines. Although the Germans were aware of all of this, they did not declare war. And Roosevelt could not. Why did the Germans declare war after Pearl Harbor. This does not make any sense to me.
The alliance between Japan and Germany had only one reason for Germany: Hitler believed, that the US would hesitate to step into the war against Germany, if they have to fear the war in the Pacific. Japan also hoped that the alliance with Germany would keep the USA out of the war. That is all. There was never a plan of a coordinated war. Japan did not attack Russia to help the Germans and Hitler did not even ask for it. Hitler was not informed about the plan to attack the US navy and there was no coordination with German subs or the Africa Corps. So the allaince was no reason for Hitler to declare war against the USA.
In my eyes, Pearl Harbor was the last chance for Hitler to avoid desaster. It was clear that the Us and Britain would declare war against Japan and that the Americans would urge their government to strike back as soon and as hard as possible. Would FDR have been able to declare war against Germany? I do not know.