Why's a Retired Army Lieutenant Colonel on the "No-Fly" List?

http://www.thenation.com/blogs/thebeat?pid=63406
"(Robert) Johnson, who served in the military during the time of the first Gulf War and then came home to serve as northern New York's first board-certified thoracic surgeon and an active member of the community in his hometown of Sackets Harbor, is not a terror suspect. But he is an outspoken critic of the war in Iraq (emphasis added by Vox),..."

- Vox