My basic sense of the discourse about politics (articles, comments on online news websites, blogs, TV shows, radio shows) is that a certain rhetorical mode or style unifies those on the far right and far left. It is characterized by anger at authorities on the opposite end of an ideological or demographic spectrum. The "bad guy" in this mode could be those who support a patriarchal society, those who support a racist society, Obama, Bush, Congresspeople, university administration, corporations such as Comcast or Walmart, "Wall Street", unions, mainstream media, etc. I'll call this, for lack of a better term, the "anger-laden" rhetorical style. It succeeds by invoking strong, negative emotions in information consumers (arguably, you could include discourse that invokes or reflects anxiety, but prior research suggests that anger and anxiety operate differently when it comes to news). We could contrast this to a drier, scientific, inquiry-based style (a la fivethirtyeight.com), or a style that attempts to present both sides of an issue in a relatively affect-less way (a la The New York Times or the BBC). I recognize, of course, that no sources are totally bereft of affect-invoking content or style, but that when compared to, say, FoxNews or the Huffington Post, it becomes clear that inquiry-based or relatively affect-less sources employ a style that depends less on pushing the anger buttons of the audience.
I sense that in the arena of news or discourse about public issues, the ratio of anger-laden style information to other styles of information has changed, and that this change is associated with increasing partisanship among political leaders (even while the partisanship of the overall US population changes very little).
It is entirely possible that the angry, negative-affect-laden rhetorical style was always dominant (see the rhetoric of some popular newspapers' editorials, muckrakers, etc.), but I would counter that by noting that the decline in consumption of mainstream news sources (which are more apt to favor an affect-less style) and the ascendance of non-mainstream sources (which are more apt to favor an anger-laden style) is undeniable.
Perhaps the ascendance of the anger-laden rhetorical style of conveying political/public opinion information draws in a segment of the population that didn't spend much time reading or viewing such information at all. In other words, there was always anger-laden, affect-less, and inquiry-based styles of conveying this kind of information, but fewer people overall were spending less time with any kind of political information than is the case now. Now, we have more consumption of such information, which sounds great, but actually the people who are new to the conversation are driving the demand for (and the supply of, in a market-based news environment) anger-laden information. So yes, very few people ever consumed affect-less information and they were probably always outweighed by consumers of affect-laden information, but not to the extent that they are outnumbered now that there has been an influx of new news consumers and new news sources to meet the increased demand. The ratio of affect-less to affect-laden information shrunk in response to the demands of an influx of new consumers
This change in that ratio could push moderates out of the online conversation about politics and away from offline political participation. The moderates would still exist, and any public onion poll would detect their presence and reflect an overall population that didn't go through the increase in partisanship that our leadership has undergone. There might be a spiral-of-silence effect happening with the moderates: they see that their voice isn't represented in the articles themselves or the comments sections and so they spend their time on other things: their own families, their own hobbies and interests.
Of course, any such argument lamenting this shift toward affect-laden information leaves one up to the accusation that one is pining away for "the good old days" when sensible, logical elites dominated public discourse and the political arena while the hot-headed rabble kept to the fringes. It is impossible for me to deny the historical reality that elites often dismissed arguments they didn't agree with simply by dismissing rhetorical styles that privileged emotional, subjective experiences over scientific or quasi-scientific approaches. I certainly recognize the value (and inevitability) of emotion in public discourse, and the fact that all arguments contain some combination of objectivity and subjectivity, of "hot" emotion and "cold" logic.
But I just don't see the current use of an anger-laden rhetorical style as the reflection of pre-existing public opinions and rhetorical styles that were heretofore excluded from public discourse. I see it as driving a shift in political thought and behavior, one that excludes anything other than anger (including positive-affect messages favoring compassion, affection, or understanding). And even though it is problematic to assert (either explicitly or implicitly) the superiority of cold rationality, I think its total exclusion (or even a significant reduction) from public discourse would only lead to an increased inability to see the world through anyone else's eyes, and that this wouldn't be a good thing.
But I'm in idle speculation mode here. I seek evidence of this, and I don't have much to point to right now that would suggest I'm on to something or that I'm dead wrong. Does the ascendance of anger-laden information (if it even is truly ascendant) reflect increased political participation and/or does it increase the polarization of elected officials and the disenfranchisement of moderates, lessening any chance we have at mutual understanding?