I see conspiracy theorists as an example of believing in a very unlikely scenario to boost your ego.
Suppose for a second that the Moon landing was faked. The level of conspiracy needed to do this and fool most of the people (including the Russians who would have called us out on it had we obviously been filming on a sound stage) would have been massive. You'd need engineers, scientists, government workers, astronauts, etc. All of them dedicated to pretending that we went to the Moon when we didn't. This would have to be a VERY well organized conspiracy. (Which alone should debunk this theory. Government is too inept to pull something like this off.)
Now, your normal person buys into the "faked Moon landing", but you are special. You are more intelligent and perceptive than they are. You see through the conspiracy and spot the flaws. In fact, you are so brilliant that the flaws seem stupidly obvious to you - which only elevates you more above the sheeple who buy the official story.
Of course, this also makes it nearly impossible to have a conspiracy theorist admit that he's been debunked. To admit this, the conspiracy theorist must lower his mental image of himself from "stands tall above all those stupid masses" to "actually a bit below those masses." This is unacceptable so any proof that the conspiracy theorist is wrong is rationalized away as being a) planted by the conspiracy to trick the foolish, b) irrelevant enough to ignore completely, or c) not proof debunking $MOVED_GOAL_POST.
You could load the conspiracy theorists into a rocket, send them to the moon, and they would still claim it was all faked just to preserve their mental image of themselves.