There may be a medical explanation. Perhaps the Republican daily diet of whoppers has caused organic brain rot, a variant of mad cow disease. On the other hand, their failure to accept reality might be psychological, early onset dementia resulting from excessive exposure to Fox News and hate radio.
Whatever the source, Republican disease has readily identifiable symptoms. There are ten telltale signs, core Republican beliefs that cause rational Americans to conclude the person they see ranting on TV or disrupting town-hall meetings is pathological.
(1) George W. Bush kept America safe. Republicans believe that George Bush and Dick Cheney bear no responsibility for 9/11. Evidently the attack was an act of God rather than evidence of incompetence. For Republicans, the fact the US survived proves Bush/Cheney were strong leaders.
(2) History will vindicate Bush. Republicans believe history will treat Bush/Cheney kindly. Over the next few decades, historians will write that Bush/Cheney were smart to abandon Afghanistan, invade Iraq, and piss off our allies. Moreover, historians will conclude Bush/Cheney were justified when they spied upon Americans, arrested whomever they suspected was a terrorist, and tortured them.
(3) The recession wasn't Bush's fault. Republicans believe Bush/Cheney economic policies - lower taxes for rich people, massive deficits, deregulation of the financial sector, exporting jobs to China, and suspension of environmental protections - were prudent. Republicans see no relationship between these policies and the recession that began in November 2007. They believe the downturn was the fault of a few bad apples on Wall Street and the market would have corrected itself if it hadn't been for the intervention of the Federal Reserve - a Zionist cabal - and Treasury Secretary Paulson - a closet Democrat.
(4) America needs less government. As much as they admire George Bush and Dick Cheney, Republicans feel they made a mistake getting the government involved in the financial meltdown. The correct procedure would have been to let giants like Citigroup and Bank of America fail, because the market would have adjusted eventually.
(5) All taxes must be cut. Republicans believe there is only one role for the government: to get out of the way. Reducing the size of government means starving the beast," denying it funds. The solution for problems such as high unemployment, inadequate healthcare, and failing schools is to cut taxes. Republicans believe that if corporations and the rich have lower taxes, prosperity will trickle down; the market will respond positively, which in time will remedy America's social problems. (Republicans also believe in the tooth fairy.)
(6) Barack Obama stole the 2008 election. Republicans believe that while John McCain wasn't a true-blue Republican, he would have been an adequate placeholder for their real candidate, Sarah Palin. Had McCain been elected, it would have only been a matter of time before Palin occupied the Oval Office. But McCain/Palin were cheated: Barack Obama wasn't eligible to run for office because he wasn't born in the US; the liberal media duped a majority of Americans into believing that Obama was an American, a nice guy with a populist agenda; and real Americans - Republicans -- were intimidated by Obama's coalition of leftists, homosexuals, Jews, Negroes, and "the people our parents warned us about."
(7) Obama's economic stimulus package was a mistake. While Republicans have a hard time blaming the recession on Obama, they do fault him for the stimulus package. Despite many signs the recession has bottomed out and the economy is recovering, Republican see no evidence the stimulus is working.
(8) There isn't a healthcare crisis. Republicans believe that America's healthcare system is the finest in the world, there is no crisis, and Obama's push for healthcare reform is actually an excuse to move the country into socialism. They trust insurance companies to do the right thing about healthcare.
(9) Obama has weakened our nation. Republicans believe George Bush kept the US strong and solidified its role as a Christian nation, leading a crusade to rid the world of heathens. In contrast, they feel Barack Obama has traveled around the globe apologizing for the actions of the Bush/Cheney Administration; in their eyes he has weakened America's image and made us more vulnerable to attack.
(10) Obama is a racist. Republicans believe the President's response to the arrest of Professor Gates proved Obama is an angry racist. This confirmed what Republicans suspected all along: Obama's a Muslim terrorist. That's why Republicans need their guns; they have to protect themselves from the new threat emanating from the White House.
If you encounter someone who suffers from mad Republican disease, turn off their TV and radio, and drive them to the nearest rehabilitation clinic -- even if that means traveling to the left coast.