All I mean to say is this: Suppose you say, "100 people have made arguments against proposition X, and all of them were bad arguments; therefore the probability of finding a good argument against X is some (monotonic increasing) function of 1/100."

If X is a proposition that is particularly important to people in cult C because they believe something very strange related to X, and 90 of those 100 arguments were made by people in cult C, then you should believe that the probability of finding a good argument against X is a function of something between 1/10 and 1/100.