History Lesson

I remember that in 9th grade, a history teacher sought to describe the immensity of China's population by telling us that you could line up all of the people in China, start marching them into the ocean, and the line would go on forever. At the time, I didn't occur to me that this was both a stupid illustration (is that not true with our own population?), and offensive.

Anyone else have an example of imagined genocide being used as a classroom learning technique?