If you have a problem with CNN, just read the first link, it connects directly to the study. The study clearly states that viewers of the Daily Show were found to have more knowledgeable about campaign issues than nonviewers. I'll point out the important passage for you:
Here is the complete transcript of the episode in which O'Reilly attacks Stewart. His comments are definately in context. He even claims that 87% of the Daily Show's viewers are intoxicated when they watch it--a statistic that I think he may have just made up since I can't find a source to confirm it online.
Furthermore, the stats are very meaningful. O'Reilly repeatedly referred to Daily Show fans as "stoned slackers." But the stats point out that the Daily Show fans obviously aren't slackers if they have more knowledge and more education. It totally refutes O'Reilly's claim.