Do you know just how much corn would ever be needed in a emergency, and how much exactly would be wasted in said emergency?
Regardless, and this may seem hard-hearted to some, but tough beans to those in the third world that are starving. That is the way of nature. When you can't legitimately support your own people, the rest of the world shouldn't be doing things to artificially inflate your ability to feed a population.
I have plenty of problems with our agricultural system, especially the intensity. But looking at it (subsidies) from a national security perspective, it is legitimate. World starvation is a bad reason to oppose it because of what I said in the paragraph above.
For more information on my opinion, check out
Ishmael
An awesome book that really goes in depth to the problems of uncontrolled population growth. This is a book I believe is one of the most important I ever read.