The Parasitic Nature of Evil
When we talk about "evil" as a force, we have in mind the personifications given to us by Christian dogma. In the fantasy land of Christianity, morality is simplified as a battle between masters (God = good, Satan = evil), with humans as their obedient pawns. This makes for a very simplistic world, which is, as usual, the exact opposite of the truth. In the real world, the individual takes good or evil decisions, supports good or evil values, of his own free will. The evils of Christianity are perpetuated by this ignorance of the facts.
When we speak of evil, therefore, we must always keep in mind that it is an adjective, a property, like "atheist" or "roundness". We routinely talk about what atheism means, even though it is only a property of individuals. So talking about evil is justifiable even if one does not believe in personifications of evil.
With this in mind, what can we say meaningfully about evil things - evil structures, evil values, evil actions ? Since the concept "evil" applies to an almost infinite number of referents, it might seem that they all have nothing in common apart from the fact that they hinder human values. However, that is not quite true.
One thing we can say about evil is that it is parasitic - it depends on the results of good values to survive and thrive. This is easiest to see in the case of collectivist structures (such as religions, governments, cults) and their relation to a society. A religious leader can only seize the resources or exploit the power which already exists. A king, a president, a dictator, can only exploit that which is produced by the vast majority of honest citizens. A cult leader depends on the resources of his brainwashed followers. This is why organized cults, once established, usually target the rich and powerful.
So whatever an evil structure consumes is a wholly parasitic process, and its very existence depends on the work, general moral rectitude, and continuous acceptance of the vast majority of the people in a society. It is not outright evil intentions, but rather the apathy of most people towards these harmful social institutions, which enables their flourishing.
Now let's look at some categories of actions which are considered generally evil. Theft, for example, can be justified in critical or emergency cases, but is generally evil. And yet a thief depends on the production of honest citizens - without resources to steal, theft is completely pointless. Likewise for a liar, who depends on his own credibility (as well as people's credibility in general) for his lies to have any effectiveness at all. Even killing someone out of passion, perhaps the least coherent form of evil there is, still relies on the victim being alive. There are many different kinds of coercion, fraud and lies, but these basic principles apply to all of them.
The general rule, therefore, is that evil will flourish to the extent that good values are being fulfilled in a society, and to the extent that exploitation is possible.
The more developed a society is, the more possibility there is for these belief systems to flourish. Of course, there are opposite memetic pressures also. Organized religion general tends to be selected against because scientific education, sociological education, moral education, and other kinds of education are enemies of belief in organized religion.
A related fact is that people with the most resources to waste are more likely to be victim of these belief systems. Rich white young students are a prime target for political beliefs, cults and religious fundamentalism. "Spiritual seekers" tend to be disaffected rich white people. This is not hard to understand. People with the most resources and the most free time have the most resources to devote to unproductive, or even counterproductive, tasks.
Evil, therefore, is parasitic. This means that evil is destructive, and in the long run self-destructive. The latter is true because most forms of evil lie outside of the context of rights. I don't want to get too much into political concepts (at least not in this entry), but the basic principle here is that evil actions are usually not self-inflicted, because people are inherently self-interested. Evil actions are therefore committed by people who have no interest in preserving that which they are exploiting, and so they will eventually destroy it if left unchecked (in economics, this is called the Tragedy of the Commons).
This phenomena also applies to religion, if we look at religious and cult leaders as agents of memetic infection. By spreading their religious memes around, they are exploiting resources which do not belong to them. Therefore they have no interest in sustaining their existence, and societies infected by fundamentalist religions can become outright non-functional (and the same applies to dictatorships as well).
Evil structures also thrive on subjectivity, especially moral subjectivity. Anything can be justified as long as you can undermine people's confidence in their own reasoning, and reify some collectivist concept as the absolute truth. Organized murder committed by a supreme being, or in the name of a country, or in the name of one religious sect against another, can be made magically moral in the eyes of believers.
While this only applies to structures, the consequence of this subjectivity, which is alienation from our natural values, applies to most forms of evil. Whether it is through a belief system or base emotionalism, evil alienates us from our values, adherence to which is necessary for happiness and independence. It reduces the individual, and by extension society, to impotence, moral tension, guily, destroys his life, and leads to social warfare.