I don't really disagree with the concept in the post, other than to say that it's always assuming that there's some information (observations) coming in on any given topic. The nuance I'm arguing for is that truly partisan news is often as much a practice of complete omission than inaccurately reported observations -- something that's....umm....omitted here, thus providing a salient example. This results in an over focus on belief networks and switching beliefs, when the result is more complex.
Many people hold no particular beliefs whatsoever on most topics. When pressed they'll generate a "belief proxy" at random until the partisan sources their mental models are fed by gives them an observation to hold to. It's perhaps not mathematical, but it's highly observable -- particularly on topics that are likely to be highly partisan.
