I don't know...a walnut is rather too large to describe some brains. Perhaps "the size of a peanut" would be more accurate?
Gagdad Bob at One Cosmos defines the problem exactly, and notes that the attempts at self-medication only excacerbate the problem :
And this is why it is so easy to be a conservative, because you no longer have to contort yourself with so many lies in order to be thoroughly consistent, both internally and externally. The left confuses their contortions with "nuance," but nuance is simply the left left brain's feeble attempt to keep reality at bay, which inevitably seeps in through the walls, ceilings, and floorboards. Or as Randy Newman sang,
Guilty, baby I’m guilty
And I’ll be guilty the rest of my life
How come I never do what I’m supposed to do
How come nothin’ that I try to do ever turns out right?
You know, you know how it is with me baby
You know, I just can’t stand myself
And it takes a whole lot of medicine
For me to pretend that I’m somebody else
This medicine is called leftism, but it has never actually cured anyone, much less a nation of people. Instead it rapidly worsens the disease it is intended to cure, so that greater and greater doses are required until the patient perishes -- if not literally, then in spirit, as we see in western Europe.
"It takes a whole lot of medicine for me to pretend I’m somebody else." Yes, it takes a whole lot of affirmative action for the leftist to pretend he's not a racist, and a whole lot of diversity to pretend he isn't intolerant of dissent. It takes a whole lot of coddling illegal immigrants to pretend they don't just want the votes, and whole lot of global warming to pretend they don't want to undermine the engine of global capitalism and progress. It takes a whole lot of outrage at President Bush to pretend they aren't allied with the Islamo-fascists, and a whole lot of talk about the "little guy" to pretend they aren't filled with class envy. And it takes a whole lot of multiculturalism to pretend they don't hate American culture and values, and a whole lot of fearful talk of separation between God and state to pretend they don't hate the former and love the latter.
Yeah boy, it takes a whole lot of moral relativism to pretend they're not immoral, and even more education to pretend they're not wrong.
There are far more complicated clinical terms for the kind of "nuanced" behavior Bob describes, but I don't have time today to go into any depth (see here and here if you are up for it) ; so I will just say-- with compassion and concern, of course-- that these people are nuts! and leave it at that.