The most difficult subjects can be explained to the most slow witted man if he has not formed any idea of them already; but the simplest thing cannot be made clear to the most intelligent man if he is firmly persuaded that he knows already, without a shadow of doubt, what is laid before him.-Leo Tolstoy, The Kingdom of God Is Within You
Tolstoy's observation likely garners a hearty "Amen!" from just about everyone who comes across it; we can all think of people who simply refuse to acknowledge any facts that contradict what they have already decided must be true. Many of us could no doubt brainstorm a long list of ways in which the above applies to most of the evangelicals we have known. Those evangelicals, in turn, would probably present us with a similarly lengthy list.
Left or right, libertarian or socialist, Christian or atheist, and so on - it's simply human nature for us to reach conclusions on certain issues and then consider the matter settled. Even those who have moved beyond Stage Three in their personal development need to guard against short-sightedness. The best any of us can do is honestly acknowledge our own limitations and strive to remain open to new information, all the while extending the same grace to our opponents that we hope to receive when we are proven wrong.