Why Do Liberals Believe What They Believe? - A similar question can be asked on Huffington Post or Daily KOS "Why Do Conservatives Believe What They Believe?
If you think Liberals are closed minded and conservatives are not, or liberals believe things that are factually wrong and this a partisan phenomenon. You are delusional.
If we take away liberalism and conservatism and re-frame this discussion as human beings. "Why we believe what we believe" then we will see this in a different light.
I recommend the book "Why We Believe What we Believe" by Andrew Neuberg. A neuroscientist and neurologist at UPENN. It is a non-partisan book that looks at how human beings think from a biological perspective. It doesn't matter if you are left or right. We are first human beings and we think and believe the same way. So the criticism of the way liberals think is really the way we all think and believe.
The book talks about from an evolutionary perspective, we evolved to be closed minded. We trust our believes more than facts. It is very hard for us to change our mind. Especially when we associate ourselves with people and groups that reaffirm our beliefs it becomes imprinted in our minds and becomes harder to change our minds.