Your both right, it's almost impossible to argue with a bull-headed individual. A waste of time, as they will always win. You may even be fooled to think that they listen to your side of an arguement, but it's all an act, they have written their agenda long before the arguement began. However, theres no need to label them as crackpots or eliminate them. Infact, they could be of the brightest minds around, it takes brains to twist words around and argue a point with no real facts. Also, they can be very kind individuals if you bow down to them and wash their feet.

P.S - Marco brought up a good point about the books, merchandise, ect. You really have to wonder how many people are motivated by the money or by their beliefs.