Sure! Why not? I find exercise helpful and took Tae Kwon Do classes for 6 years from the age of 24-30.
We know of several professional athletes who have crohn's disease during their playing years, including WWF wrestler George the Animal Steel, NFL QB David Garrard, NHL hockey player Kevin Dineen, and NFL offensive lineman Matt Light.
http://espn.go.com/boston/nfl/story/_/id/7903017/matt-light-reveals-decade-long-battle-crohns