I do not believe I have ever before linked to an OpinionJournal editorial in a fit of unadulterated agreement.
To begin with, there is abundant evidence that extreme political opinions lead to the personal demonization of fellow citizens. Consider, for example, how those on the far left and far right respond when asked for a zero-to-100 score of their feelings toward people with whom they disagree politically. Political scientists find that scores below 20 on these so-called feeling thermometers are very unusual--except on the political fringes. Indeed, according to the 2004 National Election Study, one in five "extremely liberal" people gave conservatives a score of zero, a temperature you or I might reserve for Osama bin Laden. The same percentage of "extremely conservative" people gave liberals a zero.
Ironically, these angry folks tend to feel that they are more compassionate than others--while their personal actions tell a different story. Take people on the far left. According to the General Social Surveys in 2002 and 2004, those who say they're "extremely liberal" are 20 percentage points more likely than moderates to say they feel concern for less fortunate people. But this doesn't appear to translate well to a deep concern for any individual: This group is also 20 points less likely than moderates to say they'd "endure all things for the one I love." To some, this might support the stereotype that the far left loves humanity--but only in large groups.
Like extreme liberals, extreme conservatives are more compassionate in theory than in practice: They are slightly more likely than centrists to say they "feel protective of people who are taken advantage of." Unless, it seems, they are the ones taking advantage: It turns out they are substantially less likely than moderates to act honestly in small ways, such as returning change mistakenly given them by a cashier.
It may or may not be that extreme politics is by itself what makes a person angry and uncompassionate; but it certainly cannot be improving the situation. After all, the partisan political machine today is geared toward the destruction of opponents--to convince us that the other side is not just misguided, but evil. Mounting evidence that adherence to extreme political attitudes correlates with a fundamental lack of compassion is not encouraging for the future of our civic culture, as long as rage is used as a political device.