What does Rita know except what some of the freepers are calling in to tell her and Fox. The camp is open to any one who pays thier money. Its used by paramilitary types and police. Could a terrorist have trained there? Sure, you pay your money for entrance, pay for the bullets and pay for the training. No conspiracy. Just profit.
Perhaps, like the flight schools? Or perhaps more is involved - someone has posted an article tonight about a British citizen who was tried for running terrorist combat schools in the U.S. but I believe was acquitted because that "type" of training is legal here. That's off the top of my head, but I can go look for the article if you want it.