Nonbelief is the realization that one has been cheated.
What do I mean by this? Most nonbelievers identify themselves as such because they go against belief systems which are accepted by the population at large. This means that the individual, growing up, probably experienced extensive indoctrination, propaganda and social pressure. When you become a nonbeliever, you see these things in a very different light from when you still believed. The nonbeliever realizes that he has been lied to and cheated constantly.
But beyond that, he also realizes that the very system of things is wrong or twisted. What seemed like the natural order of things now become, to the paranoid, a global conspiracy, and to the more level-headed, global dysfunction.
The nonbeliever is therefore justified in thinking that he has been cheated from living a more truthful and moral life than he could have. If the system of things that sustains the belief system did not exist, his life could have been better.
However, this also applies to believers looking at nonbelievers. Remember that the main role of the belief system, to the eyes of the believer, serves a role of moral and social cohesion. He believes that belief systems are necessary for the maintenance of morality and society. He also has been through the same social pressures.
His whole life, he has been motivated to keep believing because belief is necessary. The existence of nonbelievers, therefore, is an invalidation of what he has been taught his whole life. How can people live morally and happily without belief, when all his life he has been taught that belief was necessary to be moral and happy? When he was abused in childhood so that he would believe?
To accept that nonbelief is a viable option is to invalidate all that, and this is not an option for most people. People find it very hard to admit they devoted their lives to a lie, unless the lie becomes so outrageous that they can no longer keep deluding themselves.
Because of this, the very existence of nonbelievers is inherently offensive to the believer. Like any and all reminders of abuse and forced indoctrination, of incipient evil, they must be stamped out. If nonbelievers can be good people and productive members of society, then all of it must be useless. So the existence of nonbelief is a strong implication that there is something majorly wrong with society. This is also difficult to accept. Once again, rather than accept major flaws in what we believe in, most of us would rather continue to delude ourselves.
This is also why atheists are portrayed as know-it-alls and as “thinking they are better than everyone else.” This is easy to understand when we look at it from a memetic perspective. Since the existence of nonbelief implies some major dysfunction in society, people who drop belief altogether must think they are better than the society which perpetuates the belief system that has been rejected. Agnostics, on the other hand, are seen as simply indecisive, as “lost sheep.”
Nonbelievers are the most hated of all, because they outright refuse to play the game. As long as you accept the framework of religion/democracy, there is some tolerence between factions. As long as they accept some master, they can get along. Doctrinal differences are only relevant insofar as they separate the different factions and make them relevant. But people who refuse to play the game altogether are seen as clear outsiders, clear opponents of all that the believers, whatever their factions, have in common: moral submission, social cohesion, group identification.
In reality, of course, it is nonbelief that is most conducive to social cohesion. One will easily grant that believers experience cohesion, within their own group. But group cohesion does not necessarily translate into social cohesion. Just to take an extreme example, I’m sure the KKK is a cohesive group, but does it raise social cohesion as a whole? I rather doubt that.
Nonbelief promote social cohesion above group cohesion because it eliminates moral submission and restores moral responsibility to the individual moral agent. Collectivist belief systems promote confrontational attitudes, us v. them thinking, and social dysfunction in general.
The nonbeliever, of course, is not perfect, but at least he’s saved.