Very good point. Many people tend to confuse "open-minded" with "credulous" or, at worst and as you say, "gullible". Thus they leave themselves wide open to cynical manipulation, then stand around wondering what just happened.
At the age of five, Skagra decided emphatically that God did not exist. This revelation tends to make most people in the universe who have it react in one of two ways - with relief or with despair. Only Skagra responded to it by thinking, 'Wait a second. That means there's a situation vacant.'