I think the term 'conspiracy theory' has been turned into a blanket purjorative, similar to terms like 'socialism' or 'atheist', that serves the purpose of shutting off critical thinking when people are discussing or debating.
History is full of conspiracies that actually occured and are well-documented. The assassination of Julius Caesar and Abraham Lincoln are both historical conspiracies. The crimes of Enron were conspiratorial. Rupert Murdoch's reporters conspired to obtain personal information illegally.
The rich and powerful in the world collude and conspire all the time to manipulate or to attempt to manipulate events, with varying degrees of success. When they conspire together, they don't call it a 'conspiracy,' however...they call it a 'meeting' or a 'teleconference,' or something similar.
History is full of many events that are not the result of conspiracies of course. Many events are the result of chaos and accident.
The Official Story of 9/11 is, in a literal sense, a conspiracy theory. The US govt. tells us that a bunch of Saudi Muslims in some super terrorist organization called 'Al Quaida,' plotted, planned and conspired to crash passenger planes into buildings to achieve a terrorist objective.
The US govt. never bothered to have a trial for the alleged leader of the conspiracy, not even one in absentia, which would have been possible. This is curious, since a criminal court is usally the way one proceeds when one wants to prove who committed a crime.
In the case of war crimes, there is an precedent, the Nuremburg and Tokyo war crimes trials after WWII. Those were multinational efforts, and conducted with deliberation and without haste. The people who arranged those trials wanted the historical record of the war crimes to be very clear.
The US govt. resisted an official inquiry into 9/11 for many months, and when the govt. finally agreed to an inquiry, the panel was packed with insiders, people who had vested interests in the status quo of the US govt. When the president and vice pres were interviewed, they were interviewed together, and no recording devices were permitted...I can tell you, having been a professional investigator who has prepared reports for the cops, that interviewing two witnesses or suspects together is a very, very unsound method of investigating things! You would not interview witnesses or suspects in a shoplifting case in this manner!
When the US govt. finally allegedly caught the alleged mastermind of 9/11, he was summarily executed, and thrown into the ocean for the fishes to eat, without so much as a 3rd party objective autopsy.
Going back to the day of 9/11, there are some astounding anomalies, such as an alleged perpetrator's passport being found near one of the attacked buildings, intact, despite the alleged perpetrator and everything/everyperson on the plane being incinerated. And the astounding luck of scheduling the attack when a US defense exercise created confusion and delayed a response to the incident.
I am not saying 9/11 was an inside job. I lack the information to make this assertion.
But I am saying this: The Official Story of 9/11 contains a lot of assertions that have never been subjected to any decent objective 3rd party scrutiny. IMO, since the US govt. never put OBL on trial so as to guarantee a full examination of the crime, and since the US govt. conducted its own inquiries and allowed its own inquiries to be seriously contaminated by faulty proceedures, the Official Story is no better than many 'conspiracy theories.'
But the purjorative use of the term 'conspiracy theory' is a wonderful tool of the ruling elite. Someone starts to ask embarrasing questions, you just tell them 'We don't have any time for your Conspiracy Theories!' If it doesn't shut up the questioner, it does immediately prejudice everyone else in the room to think he is a crank on par with UFO enthusiasts.
We allow the usage of the term because it helps us avoid frightening or unpleasant possibilities.
Would members of a national govt. ever fake a terrorist attack so as to create a pretext for war? Well, the Nazis did it with Poland to make an excuse to invade in 1939. It was called the Gleiwitz Incident, and the USA didn't know the truth until the Nuremburg Trials: http://en.wikipedia.org/wiki/Gleiwitz_incident
Citizens of the USA tend to avoid the thought that the govt. could do the kinds of terrible things govts. throughout history have always done. The USA depends upon the citizens having an unspoken and unchallenged view of themselves as being slightly morally superior to other nations. And yet LBJ used radical misinformation regarding Gulf of Tonkin Incident to radically escalate the Viet Nam war, a war against a nation which posed no threat to the USA.
It saddens me that on a forum where the participants pride themselves on critical thinking that we mindlessly repeat the 'conspiracy theory' meme. Why do we want to short circuit our own thinking?
Note: I am not saying that 9/11 was an inside job. That is highly quesionable. But the Official Story is also, IMO, highly questionable. There are many possibilities as to how the crime occurred, and I think the US govt. effectively closed many possible roads of inquiry.