From Krugman's latest column:

For the last few years, the term "conspiracy theory" has been used primarily to belittle critics of the Bush administration.
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The truth is that many of the people who throw around terms like "loopy conspiracy theories" are lazy bullies who, as Zachary Roth put it on CJR Daily, The Columbia Journalism Review's Web site, want to "confer instant illegitimacy on any argument with which they disagree." Instead of facing up to hard questions, they try to suggest that anyone who asks those questions is crazy.

Rather than carefully consider the plausibility of anything that conflicts with their beliefs, wingnuts choose instead the easy route, to just abruptly dismiss and name-call (smear), typically using "conspiracy nut" or something close to it. The common-shared qualities: laziness and ignorance (the two often go hand in hand).

It's much more convenient for them to live in their Walter Mitty realities and malign anyone who would dare disturb the comfort of their respective bubbles. After all, sources of fact are deemed "liberal" and not to be trusted. Yet, isn't that mindset the height of conspiracy theory? Don't trust anything -- unless it happens to support a preconceived notion, facts be damned. True conspiracy theory involves a great deal of fantasy, and for that look no further than this administration and their very vocal supporters.