The universe is not a fair or just place. Many people do good without being rewarded or spared from considerable pain and suffering. Many people commit all sorts of evil acts without facing any sort of punishment. Some of them even profit from inflicting harm on others. In short, "karma" doesn't exist.
This is a harsh reality that we do not particularly like. It does not seem fair, and our minds rebel when we encounter evidence of it. I suspect that most of us are upset - even outraged - when we encounter something we perceive as unjust. Some people channel these feelings of outrage into efforts to bring about a more fair and just society; others prefer to call people names on the Internet. And yes, it has to be acknowledged that some people manage to do some combination of both. Regardless of one's preferred method for dealing with outrage, we can all relate to feeling outraged when we are faced with injustice and unfairness.
One of the important ways in which we atheists differ from our religious friends and neighbors is that we do not let our desire for justice fool us into imagining some sort of divine justice in an afterlife. We might not all be equally prepared to confront the reality that there is no justice in this world, but that does not mean that we must conjure fantasy worlds where we imagine justice finally being dished out. As wonderful as it might be to believe that every person would get what he or she deserved in the end, we recognize that this is wishful thinking. The fact that we want it to be true does not make it true. In fact, the intensity with which we might want it to be true is irrelevant to the probability that it is true.
The meek are not going to inherit the Earth (sorry, Rush). They are far more likely to be trampled under the boots of the powerful. The people who have been kind to others, sharing what little they have and doing their best to lead moral lives might be remembered fondly by those they leave behind, but that is probably going to be the extent of their legacy. Their rewards, such as they are, come from whatever meager pleasure they might have derived from living as they have.
Many of those who have been cruel and callous, exploiting others at every turn, will escape punishment altogether. They will never answer for their crimes because they have gamed the system effectively. Thanks to their power, status, and/or wealth, they are permitted to play by a different set of rules than the rest of us. They can commit some of the worst human rights violations and never see the inside of a prison cell.
Is this fair? Of course not! Are we happy about any of this? Hell no! But if we are honest, we have to acknowledge that it is part of our reality. And once we accept that this is part of our reality, we are free to work toward improving it. We are free to become activists, working to bring about the sort of changes we desire. After all, it is our dissatisfaction with our present reality that drives activism of all sorts.
The primary beneficiaries of a worldview that posits divine justice in the next life are those who want to minimize the sort of change we seek in this life. They do not want activism; they want complacency, conformity, and to maintain the status quo. And the more emphasis they place on belief over behavior in determining the nature of the afterlife they imagine, the more likely they are to serve as obstacles to what the rest of us want to accomplish.
