There's bias, and then there's bias. Basically, what it boils down to is that Republicans live in a Fox News bubble.
http://www.publicpolicypolling.com/main/2012/01/3rd-annual-tv-news-trust-poll.html
No, all it does is confirm the obvious. Most of the media is left wing, so the conservatives only trust the one source that isn't obviously left wing. The libs on the other hand have lots of options, so they trust all the left wing media that echo's their view, and distrust the one network that doesn't. Not surprising at all.
I personally don't trust any of them.