Some snippets from a recent article by Michael Shermer on in-group psychology. It focuses on cults as the primary anecdote for discussion, but it's easy to see how the same principles can be applied to other areas like politics or religion:
In general, these types of belief systems are coherent and logically consistent when you are inside them. It is not until you step outside the group and gain a different reference point that the coherence and logic vanishes.
Later on:
But there is something deeper going on here that I think touches on cognitive processes in all of us as members of non-cult groups, such as political parties: confirmation bias. This is when we look for and find evidence to support what we already believe, and ignore or rationalize away evidence that does not. And because we are so tribal by nature, we employ confirmation bias with extra vigor when it comes to defending the groups we belong to. Republicans tend to listen to conservative talk radio, watch Fox News and read the Wall Street Journal, gathering data and noting arguments that support their political beliefs. Democrats are more likely to listen to progressive talk radio and NPR, surf liberal blogs and read the New York Times. Everyone does it.
...later:
The confirmation bias sways us all, especially when it reinforces our inner tribalism. Most of us will never join a cult, but all of us are subject to the pull of believing that the evidence supports our most cherished beliefs. It is for this reason that we need to look for disconfirmatory evidence, to listen to the arguments of those with whom we disagree, to ask for constructive criticism of our beliefs, and to remember Oliver Cromwell's words to the Church of Scotland in 1650: "I beseech you, in the bowels of Christ, think it possible you may be mistaken."
...
I think the message that is encapsulated in those comments is very pertinent to this thread. Cromwell's line, of course, is applicable to those of any slant. But those who assume certain things about other groups, or believe their logic/beliefs to be totally coherent and understandable, would do well to consider the earlier paragraphs.
I believe ushome to be guilty of at least some of that, especially the part about making incorrect assumptions about groups based on items of information gleaned from a religious in-group who clearly doesn't fully understand opposing viewpoints as well as they might think.
Full article:
http://www.latimes.com/news/opinion/commentary/la-oe-shermer18-2008nov18,0,2806746.story