I think he has a point. I also suspect this problem is magnified due to a decline in the understanding and appreciation of tolerance as a virtue. Not tolerance as acceptance or approval, but true tolerance. Tolerance as in there is something unpleasant, objectionable, or distasteful that one nonetheless tolerates. And this is brings us back to the problem of cocooning. If we have little interaction with those of truly different viewpoints — those whose entire worldview and starting premises are different than ours — we have a harder time recognizing the goodwill and fundamental humanity of those with whom we disagree. And that means we have a more difficult time discussing divisive political issues and trying to find common ground. So instead we demonize and attempt to marginalize our opponents — undertakings that may make us feel good, but do nothing to improve the situation.I am reminded of the various "remember the good old days" essays, speaking of the 1950's and early 1960's as an idyll. Never mind the tensions, the racial discrimination and segregation, behind the scenes. Never mind the mentally handicapped child who is never allowed outside of the house or is institutionalized, lest his parents be embarrassed by the neighbors finding out about him. Never mind the ostracism of homosexuals and the criminalization of homosexuality. "We were all so much more tolerant when we were all the same. Why can't we get back to that sort of embrace of tolerance as a virtue?"
I don't want to be unfair to Adler. I'm just having a difficult time thinking of a period of human history in which the "true tolerance" he describes was lived as a virtue. Not discussed or advocated, but an actual part of the culture. I see instead a history in which differences in politics, religion and lifestyle have frequently been magnified, often with horrendous consequences for a targeted population.
Thanks to the Internet it's actually easier than ever to find and interact "with those of truly different viewpoints" - if you choose to do so. It's also very easy to cocoon. But to the extent that this represents a change, it's that people have a greater opportunity to seek out alternative viewpoints, not so much that people are largely staying within the confines of a like-minded community.
Adler argues that "It seems increasingly rare in political discourse for either side to consider that the other may be arguing in good faith", something he attributes in part to cocooning. I think a big part of the problem, though, is that many people who are leading the political discourse are not arguing in good faith. I've heard many politicians argue that they and their peers often take different positions behind closed doors than the ones that they take in public for their constituents. I've never heard a politician deny doing so. Behind the scenes we have a massive apparatus attempting to influence, manipulate and corrupt the debate.
If we're talking about people in general, it's reasonable to say that they're likely taking their positions in good faith, even if you're certain they're wrong. But when you look to the institutions that are advancing a particular narrative, those involved in the debate who are profiting from the stance they take, and those engaged in demagoguery, it's fair to both question their motives and to suggest that they're part of the problem Adler describes. When John Boehner distributed checks from tobacco lobbyists to his Repubican peers on the floor of the House, he branded himself as somebody whose motives are always in question. Does he believe the positions he takes? It's like the old joke, "Now we're just haggling over the price" - once you establish that you're for sale, your actual beliefs no longer matter.
At another level, if somebody is sincere in his support for a political position, but cannot explain why, cannot support or defend the position with facts, and cannot support or defend his position with logic, he makes himself irrelevant to the debate. We can engage in the type of tolerance encapsulated by the notion of agreeing to disagree, but you're not going to have a productive discussion if "tolerance" requires continuing to include that person in the debate or is contingent upon changing his mind.
It's not merely cocooning that leads academics to at times express puzzlement about how "someone of reasonable intelligence, good will, and good faith could reach diametrically opposing conclusions" - sometimes it's a product of the academic's having thought about the issue, while the person on the other side of the debate has given the issue little to no thought, or lacks sufficient information to properly analyze the issue. If you're actually interested in having a discussion, it doesn't take long to figure out if you're talking to somebody who is locked into a position, never to be moved, or if you can have a genuine discussion. I am approaching this from Adler's perspective of "an academic vs. everybody else", but if you want a meaningful discussion it's best to approach good faith debate without presupposing that you have an intellectual or informational advantage. You don't need to assume that the other person's position is informed, well-considered or offered in good faith, but you can attempt to provide an honest audience. If you're lucky, you might even learn something.
It would be interesting if Adler gave a position of an example of issue for which an identifiable population held an "entire worldview and starting premises [that] are different than" his own. My own international travels suggest that people around the world have a lot more in common than Adler's comment suggests. I suspect that he's speaking less about an individual or culture that disagrees on pretty much everything, across the board, and more about disagreement on some number of core or fundamental issues. Religion provides a context for how two people or cultures can be locked into a set of beliefs that exclude the possibility of the other's being correct. Religion provides an excellent context for the position that we would benefit from "true tolerance". Yet, alas, it also provides a context in which we have seen an exceptional level of intolerance over the whole of human history. (Even when one or both of the religions teaches "true tolerance" as a virtue.)
So, sure, let's aspire for "true tolerance" - but even if the tolerance we generally experience in the 21st century western world is a pale imitation of the ideal, it nonetheless stands as a remarkable achievement.