Update: A personal situation again comes into play. Intelligent people, well-meaning in many ways, and not especially liberal. Yet the style is there in criticising a public figure - insulting, condescending, mean in a way that they would not tolerate directed at other groups. Yet no self-observation, because they are Good People, and while they would fess up to individual failings, accept without question that the road they are at least attempting to travel is the right one. Not much to be said.
(In addition to my usual caveats about who I mean when I generalise about liberals and conservatives, include a generational one. My estimations apply first to my own generation and the one before me. Their applicability may wane in subsequent generations.)
I have mentioned before my belief that liberal ideas are more likely to be spread socially than by intellectual argument. This is a percentage deal, of course. It may be that most ideas are spread socially rather than by force of reason, and conservatives not much different. Nor libertarians, greens, Methodists, Unitarians, or vegetarians. Could be. My observation mostly came about because the insistence by those on the left I came from was quite emphatic that they were the thinkers and reasoners, in contrast to their troglodytic opponents; this I discovered was not true, not even close, and have observed repeatedly since. Social shaming is very big there. If one imagines online or social media discussions as a cocktail party, one sees the same type of persuasions in play: uncomfortable silences, we don't say that here, the best people assure us darling - the many social signals people give to tell you that you are going over like, well like a skunk at a lawn party. Like a turd in the punchbowl.
I think it is important to mention that this does not seem to increase as one moves farther left, nor grow fainter as one approaches the center. If anything, it is the less strident, kindly people who care about strangers and social injustice who do it more than the extremists.
On the right, being declarative is more the norm, and I think this does increase the farther right one goes. Go far enough out the trail, and you find people who make confident assertions about more and more opinions. There are people on the left who do this too, just as there are conservatives who will treat your unfortunate opinion as more of a faux pas than a falsehood. I know exceptions both personally and by what I read around of these methods of persuasion.
But it leads to further theory: do people gravitate to their politics because the culture or method appeal to them, or suit their abilities. I pick up social signals well and that was a lot of my stock in trade when I was a man of the left. Did I abandon the left because I was unwilling (or constitutionally unable) to make my arguments that way, being a more blunt and declarative person? Was any of my move rightward - or outward, upward, anyway - attributable to rejection of that style?
It's the lack of self-observation that gets me - the failure to see that insult has been given when it was clearly the only possible point of the comment; followed by thin-skinned being insulted oneself when the obvious is pointed out. I never seemed to get over that discovery in the 1980's. Yet I have to admit, that's not a logical argument for political premises either.
My son pointed out that country music seems to have degenerated over the last ten years into too many songs that are just lists of things the singer claims to like about America. They tick off the boxes and plant (another) flag in the ground declaring that this is who we are, dammit! It's pretty consistent right-wing fodder at this point, and not our best stuff. Those are tiresome to the point of head-banging sure, rather like a politician who works in all the hot-button categories he can at a campaign stop. (I heard Al Gore do that really well in 1988.)
Yet the cultural left has its lists as well, just delivered differently, letting you know that they like NPR, working in the arts or humanities and supporting public funding, having people who look very different in the same picture, public health, international understanding - those are just harder to put into a song.
And further - it has been remarked by many that there is a high-school cool kid condescension from the Maureen Dowds, the Frank Riches, the TV talking heads, the Clintons and the like. I wonder if this is part of the pattern. Wer these the kids who caught the social nuances, down to the most subtle, of the bright kids and coolest teachers, and gravitated to their culture because it was one they could succeed in? Was this reinforced by the similar styles of academics, especially in the social sciences and the arts, creating a powerful identification that just naturally extended to their political and social fashions? I will have to relook at the Jonathan Haidt summary data to see if there's anything there.
You kids who went to Christian schools, there may be muddied waters or even reversals on this. There is also a possible conservative counterpart, which I have only dimly worked out to this point.