What does the quote, "hungry men are angry men," mean in the context of World War II Germany?

It meant then, as it does now-- that if you are hungry. you are not going to be happy. I don't mean hungry the way you get when you skip breakfast and have a late lunch. You're not going to be happy, or productive if you can't afford to eat.

It was a hard time in the world and the common family has trouble buying food. If all of your money goes to rent and food, then how can you afford to buy anything else?

This isn't an ancient problem that only poor people in other countries have. This is an every day worry for millions of americans.

People are happy when they have food, home, and the time and money it takes to enjoy their hobbies. Just imagine that there are no jobs. You are starving, not just for the day, but all the time. You can't find a job. Your kids are starving.

Someone comes around and tells you they know a way to make things better. Put food in your belly and wine in your cup. You're going to listen to that guy.

What does the phrase "Hungry men are angry men" mean in the context of World War 2?

This quote has a literal and figurative meaning.  Literally, if a nation has citizens who are starving or impoverished, they will look for someone to blame.  When no one comes to their rescue (such as in Germany during their depression), they will rise up themselves or follow someone who directs their anger toward a target (again in Germany, Hitler used the Germans' anger over WWI's aftermath and their economic depression to kindle anger and hatred for the Jews).

Figuratively, if someone is hungry for power, attention, etc., he or she often becomes angry toward whoever or whatever prevents that person from obtaining power or attention.  Shakespeare uses this idea when his Caesar says that he "likes not [Cassius's] lean and hungry look"; he would prefer to be surrounded by fat men.  He knows that Cassius wishes him ill will and that "fat men" are satisfied men.  They have no reason to be angry toward their government, leader, or country.