Right, because there is no negative coverage of Democrats and no positive coverage of Republicans. Taking your Kool Aid intravenously now, I take it?
I think the problem with nutters is they are so immersed in their faith they cannot do even semi-objective self analysis. When they see a negative story about the left, they don't see it as bias. They just nod their heads and say, "Damn right." or "It's about time they got one right." When they see a negative story about the right, however, they wind up the outrage and start shrieking, "See! BIAS! BIAS! BIAS! Damn librul media durr."
One reasonably scientific study of media bias I read tends to support this. It found Fox to be right-biased, MSNBC left-biased, network coverage reasonably unbiased, and CNN relatively unbiased but more negative overall. I think that why the right sees CNN as so liberal, because it has been quite critical of both parties. They ignore the negativity towards the left, obsess about the negativity towards the right, and conclude in their partisan haze that CNN is the problem.