"Truthers" are people who believe that the government is wrong or lying about something, and the "Truther" believes he or she knows what the "truth" really is.
After studying and arguing with "Truthers" for over 11 years, it seems to me that "Truthers" can be divided into two sub-classifications: Conspiracy Theorists and True Believers.
Conspiracy Theorists generally believe that the government is deliberately covering up "the truth" about some event for evil, manipulative purposes as part of some massive conspiracy. The Conspiracy Theorists generally believe they have seen through the plot by spotting similarities to past known "conspiracies."
True Believers generally do not believe that the government is covering up the truth. Instead, they generally believe that the government and everyone in it is just incompetent and cannot figure out the truth. The True Believers believe that they (and everyone who agrees the government is wrong) have figured out "the truth."
Professor James Tracy, for example, is generally considered to be a Conspiracy Theorist. He sees the government as having concocted various complex plots with the cooperation of the media (and everyone else required to make the theory work) to mislead the American public in order to manipulate them into accepting some new program or law -- gun control being a prime example. He fantasizes such government conspiracies as being behind the Newtown massacre and the Boston Marathon bombings. His argument is that those events were just staged "enactments" made to frighten and manipulate people. And, he seems to believe that anyone who disagrees must be part of the conspiracy. If proof is found to debunk his conspiracy theory, he sees the proof as proof of his theory, since it means the government has planted false evidence in an attempt to debunk his theory.
Other individuals believed or considered to be Conspiracy Theorists are Professor Lance deHaven Smith (whose theories are very similar to those of Professor Tracy), Professor Francis Boyle, Dr. Barbara Hatch Rosenberg, author Edward Jay Epstein and numerous others.
One unusual but telling fact about most Conspiracy Theorists and True Believers is that they very often think that all other conspiracy or similar theories are ridiculous and totally unlike their own. 9/11 Truthers often think Anthrax Truthers are stupid, and vice versa. Sometimes, to avoid using the word "conspiracy," the "Truthers" will argue that the manipulations could be the work of just one key criminal who does all the thinking, and countless government underlings simply go along and do as they are told.
On this forum, "Anonymous" is clearly a True Believer, since he never talks about any "conspiracy," only about how the FBI is wrong in pointing at Dr. Bruce Ivins as the anthrax mailer. His mantra is "Amerithrax represents the greatest intelligence analysis failure in the history of the United States." "Anonymous" clearly feels that he knows the "truth," even if he cannot provide any solid facts and doesn't seem to be able to fully explain his reasoning.
R. Rowley appears to be another True Believer - but at times he also seems to be a conspiracy theorist. He also never talks about any government conspiracy, but he has a theory that the anthrax letters were sent by some mastermind, and many other hoax letters and other types of mysterious letters were sent by the same person or by fellow conspirators. And, of course, only Mr. Rowley has been able to figure out the "truth" about how all those happenings are connected.
One attribute that seems to apply to all Conspiracy Theorists and True Believers is that they have a double standard for evidence. If the "evidence" supports their theory, anything goes. If the evidence disproves their theory (or helps prove a different theory), they set very strict and often unrealistic standards for what they will accept as evidence.
Another attribute that applies to nearly all Conspiracy Theorists and True Believers is that they do not like being labeled as "Conspiracy Theorists" or "True Believers," since that puts them into a category with many others with whom they do not agree. Generally speaking, each individual Conspiracy Theorist and True Believer has independently developed his own theory. Therefore, since they have a "unique" theory of their own, they feel they are unlike all other Conspiracy Theorists and True Believers. In reality, that makes them just like all other Conspiracy Theorists and True Believers.
Yes, we all know there have been people who had facts about some event that might happen, and in hindsight, more attention should have been paid to what facts they had. But they had FACTS not beliefs. So, they weren't Truthers. And, too, real conspiracies have been uncovered by reporters and others digging for facts - the Watergate Scandal being the prime example. Those people produced FACTS to dispute beliefs. "Truthers" argue beliefs to counter solid facts. Or they present their beliefs about facts. And, they usually want the FBI to do the investigating for them to prove that they are right.
For every person who truly knows facts that no one else knows, there seem to be thousands of "Truthers" who only believe they know "the truth" but have no solid facts to support their beliefs.