There have been a few books and articles written recently characterising liberalism as a sort of mental illness. I haven't read any of them. I certainly have some sympathy with the idea that there are psychological mechanisms that prevent liberals from seeing some aspects of reality, but mental disorder seems a bit of a reach.
I could cheat and say that my experience arguing with progressives has some similarities to my discussions with the mentally ill, but that would be choosing my data conveniently. In fact, most of us act about the same when confronted with an idea we think is wrong, ill or not. As frustrating as it is to try and get psychotic people to admit the possibility of a different interpretation of reality, it is actually not that different from all rationalization and evasion.
Here's the interesting question: in psychology, we are presented with people who have been told a thousand times their ideas are crazy before they get to our facility. They've been told but they haven't believed the tellers. Our job is to get them to accept, however partially and grudgingly, a set of facts that everyone around them can see (even other psychotic people) without effort.
Play that out in political persuasion. I contend that liberals simply do not understand conservative arguments. They think they do, but they cannot accurately repeat them back. They are usually unable to describe them without caricature. Yet even in an MSM saturated subculture, they must have heard the opposition arguments a hundred times. What prevents the hearing?
No cliches, please, unless you are willing to give some explanation or evidence why the cliche is true.