You know, whan I see a stage magician, I see an amusing con artist, a trickster, someone who likes to decieve people. But others see an expert on science.
From a behavioral psychology perspective, what is the motivation for a person such as James Randi to be honest? He is rewarded (money, acclaim) for his ability to trick people. He makes a living at it. Such a reinforcement is a powerful incentive to continue tricking people. And even when he's apparently being honest and forthright, the behavioral training is still in effect. He may even believe himself to forthright and honest, but the pattern is set. Once a con, always a con.