I think it misses one step.
Liberalism is not a personal disease. A man confined to solitary confinement can still get sick and die from the plague, exhibiting the same essential symptoms and disease progression as a man in the public light. But the essential qualities of the Liberal disease that afflicts our cultures are not manifestly present in that solitary confinement cell, even if it be Hitler, Mao, Stalin, or Hillary Clinton wishful thinking ;) who resides there.
Rather, Liberalism is a sickness of society, not of the individual. Granted, as with most disease, weakness in other planes of ones life makes one more susceptible to infliction. People with the ego weaknesses that Mr. Ray describes are more likely to be dangerous liberals, but that is just a statistical tendency, in the large.
What would be of interest to me would be to further study Liberalism as disease of the body politic, a social or communal (note the common root words with "socialism" or "communism") malady. I have this hunch that like most diseases, there are several essential different elements or roles that contribute essential elements to the overall dynamic, like the tasks of the stage hand, the applause of the audience, the parts played by the actors, the guidance of the director, and the funding of the wealthy benefactor, to a Theatre Play.
Some of these roles, most in fact, might be typically played by quite ordinary people with no particular psychological weaknesses. Some of these roles, such as that of the Grand Tyrant (Hitler, Mao, Pol Pot, Stalin, Napoleon) are likely played by exceedingly warped individuals.
But it is the identification of these roles, and the illumination with examples from our history of how they interact to produce the overall phenomenon, that is of particular interest.
Indeed, if we can better understand this disease, perhaps we can better fight it. Surely it is the most lethal disease afflicting mankind.
You state that liberalism is not a personal disease. I say liberalism is a personal disease. The disease they have is actually hypocrisy. The only way liberals could say one thing but do the opposite is because they are hypocrites. They have one standard for themselves and another standard for others ie a "double standard".
To say that it is not a personal disease is to confuse cause and effect. The person in the solitary confinement cell still has the disease (hypocrisy the cause), he just doesn't have a group to operate with (liberalism the effect).
By the way thank you for posting this wonderful and insightful article ThePythonicCow. And thank you johnjayray for the tremendous amount of research and thought it took to produce what I consider a masterpiece.