The question I would ask – and the irony of the whole conspiracy meme – is that the various things that they say that believe are in contradiction to each other.
On the one hand, the conspiracists tend to think that the government is ineffectual and corrupt and staffed by incompetent idiots.
Yet at the same time, these conspriacists believe in things that would required extreme coordination, extreme competence, split-second timing, and brilliant planning. And on the continued silence of tens of thousand (or more) people essentially forever.
[Just look at 9/11. If that was a US government conspiracy, look at all the thousands of people that would have to have been in on it, from the airlines to the pilots to the US army and Air Force, to the Congress and the Executive Office – and then all the way down to the NYFD, the FBI, the Pentagon employees, and so on. Not only would they have had to be in on it, but 12 years later, they would have to keep silent. That’s just not realistic.]
So to the conspiracy lovers, I would ask “How do you square your allegations of government incompetence with the utter success of the conspiracy?” – and the answer would be “I can’t” – because there is no conspiracy.