The significance of Dan Holmes' question about conspiracy theories goes beyond Ricochet's Code of Conduct--it's a fascinating question.
I'll begin at the end of the argument and explain, first, why our Code of Conduct aims to discourage them. Let's start with the Ricochet founding legend. (Like all good founding legends, it happens to be true). A couple of talkative, good-natured, right-of-center, fun-loving guys were sitting around one day talking about politics and the Internet, and saying, "The thing is, where can you go to talk about this stuff and not waste your time getting into a flame war with the tinfoil-hat brigade?"
To an extent, our definition is like Justice Stewart's definition of pornography. We know a rhetorical rathole when we see it; the whole point of Ricochet is to avoid conversations that go over the same ground without getting anywhere, shed more heat than light, and leave everyone feeling that it's time to change the channel. So the point of banning most conspiracy-theory talk is not to prevent the truth from outing, but to keep the conversation interesting.
But that leaves the more interesting question unanswered: Is there in fact a definition of a conspiracy theory more rigorous than "We know it when we see it?"
Of course there are real conspiracies, even in open societies and liberal democracies. Dan brings up the perfect example--the conspiracy to "hide the decline." That was, we can clearly see now, a genuine conspiracy. Many people who had been dismissed as tinfoil-hat-brigade types turned out to be absolutely right. That's why we say "99 percent" of conspiracy theories, not "100 percent."
But most conspiracy theories are just deeply implausible, and require a view of the way the world works that is so counter to common sense and experience that it can't really be viewed as "conservative."
I live in Turkey, so I actually spend all my time trying to explain to people why their pet conspiracy theories are implausible--particularly when these theories concern America, probably the world's least secretive society. The belief in conspiracies is obviously closely connected to lack of transparency in government. If you can't see how things really work, it's impossible to come up with a good mental model of how they don't work.
When I argue with people here (as I do all the time) about conspiracy theories, I find that the following points seem to make sense to some people, sometimes.
1) It is incredibly hard to keep secrets. The logic of this point is intuitively appreciated by any man who has ever had more than one girlfriend at the same time.
2) The more people who know the secret, the less likely it is to stay a secret. This is why men who have more than one girlfriend at the same time usually try to keep the circle of people who know about this to a minimum.
3) It is highly unlikely that a major political event would happen owing to the agency of a very small number of people. Think about the manpower required just to make a small thing happen--to run a corner grocery store, for example. The bigger the thing you're trying to do, the more manpower and expertise you need. If you're going to stage a coup, control the currency markets, take over the media, or assassinate the president, you're going to need a big staff. Therefore, it is incredibly unlikely that conspiracies will stay secret.
4) It is incredibly hard to organize anything. Most people grasp this intuitively. If it were so easy to organize people, no one would ever get stressed about planning a wedding.
5) It is incredibly hard to get people to work effectively toward a goal. Anyone who has ever managed a small business knows how hard it is to get employees to do what they're supposed to do even when the goal is clear and even when everyone knows what they're supposed to do and why. To pull off even a modest goal in business, you need sophisticated communications, training, a management hierarchy, accountants, endless meetings. It is extremely hard to do even when you don't have to do it in secret. Adding the imperative of secrecy to such an operation would make it exponentially harder--and thus less likely to have happened.
Those are just some basic, obvious points that are easily confirmed by the personal experience of every human being who has ever had any contact with other members of his species.
The mark of a conspiracy theory is that is assumes the world works in a way that runs counter to these observations: It assumes a very big secret that many people know but none reveal. It assumes the people keeping this secret are better-organized, more competent, and more effective than any of our experience of life suggests people to be. And it assumes this, usually, in preference to a vastly more parsimonious explanation of the event in question.
Those are some general thoughts, which we can probably refine here. But the basic answer, from Ricochet's perspective, is that a conspiracy theory is one of those ideas that makes us say, "Oh, man, not that again. Must we waste time talking about this? Wouldn't it be great if someone set up a website where people could talk about right-of-center politics without having to deal with the flame wars and the tinfoil-hat brigades?'"