They claim a sort of monopoly on rational thought, but so many of the premises on which they build their worldview are so flawed, that their conclusions are a muddled mess of greed and delusions of self-superiority.
Where it gets sticky, is that the atheist has no higher authority from whom/which he/she may derive morality. The theists know this, and accuse us of being guided by situational ethics
. Unfortunately, this is to some extent true. There is no absolute 'higher' reason why people can't choose to be greedy, selfish or even murderous.
A hot-house philosophy like Rand's, a myopic view of history, and a fundamental misunderstanding of how societies flourish and how people interact leads some people to conclude that they are free to behave only in their own self-interest.
Their mistake lies not in their conclusion but in the means by which they arrived at that conclusion. When dubious untested and untenable theories are discarded, when history is studied properly, and when efforts are made to understand human behavior and interaction, one will realize that it is in fact in one's own best interest to be kind, generous, mindful of the environment and humane. Not only will one benefit from living in such a society, but that society will be preserved for one's progeny, which shall meet the needs of one's own genetic legacy as well as that of the species as a whole.
We are sometimes duped into trying to make our ethics match the xian morality that has held sway for two thousand years. If we can only craft an ethical code that arrives at the same place, we would be safe from recrimination by those who claim the high ground based on their religiosity
. We don't have to do this. We should not do as the Creationists do; work backwards from a conclusion in an effort to effect a cause. We don't need to do this. The reasons for moral or ethical behavior are self-evident They require a long view, perspective. They are not black and white. They are difficult and nuanced. Harder to grasp than ten laws carved into a stone tablet. For the more pressing concepts, man-made laws, judicial systems, systems of checks and balances in government and so on will have to suffice.