Ted Goertzel, a professor of sociology at Rutgers University who has studied conspiracy theorists, said “there’s a similar kind of logic behind all of these groups, I think.” For the most part, he explained, “They don’t undertake to prove that their view is true” so much as to “find flaws in what the other side is saying.” And so, he said, argument is a matter of accumulation instead of persuasion. “They feel if they’ve got more facts than the other side, that proves they’re right.”
I've seen so much evidence of that particular intellectual strategy that I have to say I know a number of those "other groups." And I think that criterion may be useful for the ordinary person trying to decide what or who to believe. Do they spend all their time attacking others? Is there any positive reason to believe what they say? That's one way to tell science from conspiracy theory.