Some years ago I remember seeing a very convincing documentary (can't remember the subject). I found it convincing because I couldn't really find significant flaws from the arguments presented. I was, however, soon introduced to some actual facts about the subject matter, and suddenly the arguments of the documentary seemed to crumble. This got me thinking about WTC -conspiracy theorists, Zeitgeist-believers, those who believe the moon landing was faked, etc. All these people have been presented with two things:

1) Facts

2) Arguments based on the facts

It seems to me, that most people put all their attention on #2, questioning whether the arguments based on the facts seem valid. If they do, they tend to accept the arguments. The problem is that most people take it for granted that the facts presented are true. As if we're just too focused on the actual arguments to remember to question the actual facts.