I have done many posts on surveys (especially in health care) and how they are manipulated in by others as tools of propaganda (see below). This can be true of all political stripes. I have talked about how the questions on surveys and polls can skew the results. More specifically which questions are or aren't asked, how they are asked (phone, internet, in person, or mail), their wording, the sample size selection, and other things can skew the results of surveys and or polls. Even when these issues are not a serious issue, there is always statistical uncertainty in surveys. Comments are often made on 1% differences in surveys as if they are real when they are really random noise.
The surveys that Politifact site show variability in the results that they give. Giving blanket statements like the one Stewart gave can be dangerous. Media Matters published it's own analysis of the surveys that Politifact sites. I don't have time to go into the merits of the arguments today but you can apply the principles that I discuss in the related posts below to Media Matters and Politifact's discussions. Aside from this kind of finger pointing the real problem is ignorance of the facts in general. In the clip below the Fox News anchors are gloating that according the Pew research their viewers have a 20% average knowledge ahead of MSNBC by 3% and CNN by 6%. They do not say what the margin of error was.