Read here for an explanation of how the sociological concept of boundary work is applied to the issue of false equivalence in media coverage:
Boundary work is a kind of rhetorical work that is performed in public argument: something is asserted to be science by stressing what it is not (pseudo-science, or faith, or religion, or what have you). Even Tim Geithner did it in his exit interview when he painted his own work as just a kind of technocratic problem-solving rather than politics, see this analysis.
It seems to me that our political discourse also contains a similar kind of boundary work — between “politics” and “policy.” Our politicians will always say: what I’m doing is just plain old common sense or the right thing or just good policy, or just the solution to a problem; whereas what my opponent is doing is playing politics. And if one sees politics as actually a way of managing relations between conflicting groups of people, one can see why they do that.
For instance, reforming the American health care system is almost certainly a matter of redistribution: taking money from older people and giving it to others (the uninsured, younger people, etc.). But one can’t say that if one is a politician, and so there is a delicate balancing act: one’s own work is constructed as problem-solving and policy-making, the opponent is portrayed as playing politics (where politics is understood to be trading off between different social groups).
I think this kind of boundary work exists in journalism too (and more on why it exists later); it’s what you call false equivalence (and Yglesias calls bipartisan think). Here the newspaper is seen as above politics, which is what grubby politicians do. And therefore the contrast between the policy that the newspaper is advocating (which is not politics but merely good moral sensible stuff), and that what the politicians are doing. It is imperative, I think, in this model that both parties be painted in the same brush. Because if you don’t, then you agree with one of the parties, which therefore makes you political.
Why should the newspapers practice this kind of boundary work? My sense (which comes straight from Paul Starr’s history of the media) is that it’s a holdover from the times when the newspaper industry changed. As we all know now (from arguing about partisanship), newspapers in the 19th century were unabashedly partisan. They also catered to niches, and made money from subscriptions. And that changed sometime in the 20th century when newspapers started to make money from advertisements — and therefore they had to be less partisan and attract more people. Hence the objective tone of the reported stories (he says, she says) — and also I think the false equivalence of the editorials.
The concept of symbolic boundaries is an important one in the sociology of culture. Groups or organizations engage in drawing boundaries between what they are (by their own definition) and what they say others are. Policing these boundaries is a consistent and tricky task; the changes the other groups make might force a group to redraw its own boundaries. Or, outside social forces and circumstances might push all groups to redraw or double down on their boundaries. A good application of this concept to defining social class in the United States and France is Michele Lamont’s book Money, Morals, and Manners.