Ayn Rand held a kind of Gresham's Law of human thought: that bad thinking drives out good thinking. This passage in Atlas Shrugged makes her view clear:
Whenever you committed the evil of refusing to think and to see, of exempting from the absolute of reality some one small wish of yours, whenever you chose to say: Let me withdraw from the judgment of reason the cookies I stole, or the existence of God, let me have my one irrational whim and I will be a man of reason about all else -- that was the act of subverting your consciousness, the act of corrupting your mind. Your mind then became a fixed jury who takes orders from a secret underworld, whose verdict distorts the evidence to fit an absolute it dares not touch -- and a censored reality is the result, a splintered reality where the bits you chose to see are floating among the chasms of those you didn't, held together by that embalming fluid of the mind which is an emotion exempted from thought.
This view largely accounts for the atmosphere of condemnation which so often pervades Objectivist circles. If a single evasion turns a person's mind into a "fixed jury" perceiving a "splintered reality," then one must be constantly on guard against any speck of evasion in oneself and others. "Make every allowance for errors of knowledge," Rand wrote further on in John Galt's speech; "do not forgive or accept any breach of morality." To Rand, "breach of morality" meant "breach of reason."
But is reason actually so fragile? Should we regard everyone who is irrational in any respect as headed for perdition? If so, it's not surprising that Objectivists should denounce anyone with whom they have unresolvable disagreements. Either you're irrational, or the other person is -- and it can't be you.
In fact, though, we see that people can build walls around their irrationality, limiting its scope. People who accept bizarre religious notions may be exemplary scientists. Some who claim to live by their horoscopes nonetheless conduct their lives quite reasonably. Most people do some damage to their lives with their irrational premises, but few turn into raving lunatics or mass murderers. A person's level of rationality may increase or decrease.
It's difficult to try to persuade people when you equate minor irrationality with depravity. Notice that most of Galt's speech is a series of denunciations, even though he's nominally addressing people who still have some good in them. If you tell someone, "Death is the standard of your values," is there any reason he should continue listening to you? All you can do is isolate yourself from all the corrupted minds, with no hope of communication.
This premise has undercut the good which Objectivism could have done by making enemies everywhere. It led to the denunciations within Rand's own circle, and to the condemnation of potential allies such as libertarians. The choice isn't between rejecting every deviation and accepting everyone indiscriminately; judging people's value as allies depends on the degree of their rationality in the areas which are most important, and on whether they're improving or deteriorating.
I'm not offering this as a license to be irrational. They more philosophically-minded and intelligent you are, the greater the dangers of minor evasions, because your thoughts in different areas are all connected to one another. But irrational fear of irrationality in oneself is also harmful. Rand also wrote, "There are no evil thoughts except one: the refusal to think." Overcoming one's own irrationalities requires first acknowledging them without self-condemnation.
I'm not suggesting any lack of fire in condemning things which are really wrong, but the fire should be in proportion to the cause.
If anyone can pick up the pieces of Objectivism and put them back together, recognizing the error of the "Gresham's law" view of human thinking would greatly improve its chances. Optimism about people is more effective than pessimism.
The ideas for this post grew out of some recent correspondence I've had with Bill Wells.