This country has been shaped throughout its history by influential writings. From John Locke to Thomas Paine to Harriet Beecher Stowe to John L. O'Sullivan to modern-day bloggers. The problem today, with the advent of the Information Age is that we have too many. While the notion that everyone can be a pamphleteer certainly is a positive one, it also results in a retardation of the change of public opinion. With a vast number of sources readily available, people are free to simply read, watch, or listen to arguments that simply reaffirm what we already believe, regardless of how wrong we are.
An extension of this principle of ideological isolationism is the politicization of science. As the saying goes, you're entitled to you own opinions, but not your own facts. However, today that doesn't practically apply. If you want to believe that the universe is 6000 years old, or that Global Warming is a myth, or that abortion causes breast cancer, or that the unborn child is somehow part of the mother's body, you can find a city on the planet of Internetopia where you will never be corrected because everyone is just as crazy as you are.
This is even more extreme on forums where dissent results in banning, causing forum's ideological spectrum to shrink further, narrowing the acceptable viewpoints further. This eventually snowballs into situations like you see on RevLeft or Democratic Underground, where anyone (even a die-hard liberal) is accused of being "misogynistic", "reactionary", or "anti-choice".