Take, for instance, the description of "an American" friend who has provided the speaker with information about preparing humans for consumption. This gives us a general idea, though within a comical context, of the reputation "Americans" still had in the early eighteenth century for being uncivilized, veritable "savages." But it's hyperbolic. (Hopefully Swift knew that Americans were not really like this, even at that time.)
Answer:The temptation to form premature theories upon insufficient data is the bane of our profession. With this one succinct phrase, Holmes sums up what makes him so useful and so valuable. He abandons theories that do not work even if he once believed them to be true.
I believe he perceives his experience as an unpleasant one and wants to make a movie called MONSTER based on his experience and he got the name MONSTER because it's what the prosecutor called him.