Yglesias acknowledges the limits of fact checking:

The genius and the horror of something like D’Souza’s argument is that it’s perfectly possible to put together something utterly loopy that makes no factual errors whatsoever. Indeed, in some ways punctiliousness about the facts is the signature of the conspiracy theorist. Glenn Beck’s TV show is, in its way, the most fact-filled program on cable. It’s just that you can string together a lot of data points in a nutty way if you want to.