Salon headlines it,
The internet is making us stupid, but it's actually our friends who are doing it. If you surround yourself with people who all hold basically the same view, your views will skew toward the extreme end of the views you all hold. We self-select for groups of people who believe as we do: that ska is the best kind of music to listen and dance to, that only liberal Democrats are worth voting for, that the Bible holds the unalloyed truth and law for everyone. Then, once we're in this safe haven of like-minded people, according to Cass Sunstein, the author of Republic.com 2.0, we seek to reduce the diversity within our own group. We look for consensus, but instead of finding it in the middle, we find it on the ends, in the most orthodox position. The reason he's blaming the internet is because it's the latest tool we use to find others who believe and think like ourselves.
It's a good idea to try on the other person's perspective. Sometimes for exercise I practice trying on a Republican Hummer-driving military family member, to experience empathy with this worldview. It's the people I meet who don't fit my vilified stereotype that make me want to try on this worldview, but I wouldn't meet them in the places I go to find my kindred. I find them where I'm not looking, like at work. Our marketing director seems like a kind, funny, civic-minded person, who has revealed to me that she is an active Republican. Kevin tells me that many of his co-workers are active, former, or reserve military personnel; they're also nice people.
We have a friend who is more like other members of my in-group: she's queer, smart, progressive, but she drives an SUV and uses her cell phone while driving, two activities that make me want to mount a rocket launcher and a cell phone jammer on our Civic. (I know you're reading this, and don't worry, I promise I'm not going to ever bomb your SUV/jam your signal.)
I have to reconcile the worldview I cultivate in pockets like the Pioneer Valley, where vegan potlucks rule, with these real people who remind me that there are many others out there that I just write off as inconsequential, because they're not part of my clan. It's the same old xenophobia, with new labels. It's wired deep, so I have to do the work in the frontal lobes to counteract the negative effects of letting my lizard brain decide which humans are worthwhile and which I can smear with my imaginary rocket launcher.