In the beginning of the book Dune, a Bene Gesserit Reverend Mother tests Paul Atredies with the "gom jabbar", a test of life and death. When asked afterwards why he was being tested, she responds that she was testing to see if he was a human. Not in the genetic sense, but in the sense that he was a rational, thinking being.
DUmmies, in this sense, aren't "human". More so than the typical leftist, they have not developed any type of rational thinking skills -- they respond solely to stimulus, and latch onto any explanation, no matter how far-fetched, when reality does not square with their perceptions.
John / Billybob