I’ve been thinking about this as well lately, specifically in terms of reducing hatred and prejudice (racism, sexism, etc). For example, this is anecdotal, but one (black) man named Daryl Davis says that he has gotten more than 200 KKK members to disavow the group by simply approaching them and befriending them. Over time they would realize that their views were unfounded, and gave up their KKK membership of their own volition. This is an interview with Davis: http://www.npr.org/2017/08/20/544861933/how-one-man-convinced-200-ku-klux-klan-members-to-give-up-their-robes and I think there is also a documentary about him.
This is a great Vox article about a study that discusses ways to reduce people’s biases: https://www.vox.com/identities/2016/11/15/13595508/racism-trump-research-study. The article title is about reducing racism, though the study discussed is about views on transgender people. It suggests that just a 10-min, open conversation can significantly reduce people’s biases, and that these changes persist.
And lastly, another anecdotal story on how Derek Black, the godson of David Duke, and the son another very prominent figure in the alt-right, ended up leaving the alt-right after a group of diverse college classmates befriended him, and he slowly abandoned his previous views over the course of months.
While two of these links are to anecdotal stories, I think they are important in showing that even those with really extreme prejudice (KKK members and a young alt-right leader!) can let go of their prejudices when approached in the right way.
It definitely seems like an intervention that would require lots of grassroots, individual action, I suspect it could be very hard to measure the benefits of it—the amount of lives lost to this kind of prejudice and polarization is pretty low (at least in the US), and the other benefits that would arise are hard to measure. If someone else has good estimates on how impactful this would be, I’d love to hear them! Regardless I’m very excited to see some interventions in reducing prejudice and hatred that do seem to actually work, though more study into this is definitely necessary!
I don’t think the recent rise of polarization in the US over the last decade is driven by a rise in racism or sexism.
Activism to reduce either of them might be valuable, but I don’t think it solves the issue of polarization.
I bet a more neglected aspect of polarization is the degree to which the left (which I identify with) literally hates the right for being bigots, or seeming bigots (agree with Christian Kleineidam below). This is literally the same mechanism of prejudice and hatred, with the same damaging polarization, but for different reasons.
There’s much more energy to address the alt-right polarization than the not-even-radical left (many of my friends profess hatred of Trump voters qua Trump voters, it gives me the same pit of the stomach feeling when I see blatant racism). Hence, addressing the left is probably more neglected (unsure how you’d quantify this, but it seems pretty evident).
The trouble I find is that the left’s prejudice and hatred seems more complex and harder to fix. In some ways, the bigots are easier to flip toward reason (anecdotes about befriending racists, families changing when their kids come out etc). Have you ever tried to demonstrate to a passionate liberal that maybe they’ve gone too far in writing off massive swaths of society as bigots? Just bringing it up literally challenges the friendship in my experience.
I think polarization is incredibly bad, there are neglected areas, but neglectedness seems to be outweighed by intractability.