Man is a rational animal. When he is no longer rational he becomes evil.
"To know one's own desires, their meaning and their costs requires the highest human virtue: rationality." - Ayn Rand.
What causes man to become irrational?
Stalin, Mao and Lex Luther were all perfectly rational (but for most, evil) people.
So, there have been no evil men who were entirely rational? I don't think so Lev.
Its obvious that the antithesis of evil is good. Why fight it?
This is the biggest piece of Randish poppycock (and not incidentally, the centerpiece of her 'rational' thought)! First, to know one's desires has nothing to do with rationality. A pedophile likes to have sex with kids. He knows his desires just fine. A selfish person likes not to share his toys with others. He knows his desires just fine. Neither needs to emply rationality to understand those desires. And as for rationality being the highest virtue - Rand exposes herself here. If you have some scale of virtue that you can measure rationality with, you then have some morality outside of rationality. Finally, rationality can be used for good or for evil. It is neutral to good and evil. Rand desperately wants there to be no good or evil that can't be discerned through the use of reason, and she tries (in vain) to use reason to prove her point. It's like trying to prove the fourth dimension can't exist using only three.