Any large, like minded group of people who make quick, knee jerk reactions based on sheltered and moronic views and are especially vocal in voicing their outrage. This can be political, religious, automotive or sports views in nature, or any other movement.
4chan's /b/ is a particularly active breeding ground for a retarded hordes.
"Did you see that 10,000 Camaro's are being built a month?" "Yeah, just wait until the retarded hordes over at Camaro5.com's message boards hear about this"