To answer your question:
No it is not "biased". It is designed to find out exactly what it states it intends to find out. There is no deception. And as far as I can tell, it is well designed and probably shows what it purports to show.
I agree with you (see below in this thread) that there are more interesting points to look at, that they left out. Personally, I think that NPR/PBS consumers would continue to knock the sox off the Fox consumers, no matter how you slanted the questions. I'd love to know, though.