There is a fundamental inconsistency in the way many atheists relate religion to good and bad actions.
When a theist does something bad, religion is to blame. "What do you expect? You give a person a desire to please god and a belief that god is pleased by a suicide bombing or killing apostates or some other horrendous act, and they go out and kill people. Religion poisons everything. "
When a theist does something good, this is because of our inherent good nature. Evolution has disposed us towards fairness and charity. Giving people a desire to please god and telling them that fairness and charity please god, while brutality and injustice do not, has absolutely no effect on the disposition to be kind and just."
This inconsistency not only reflects an intellectual fault, but a moral failing. This is prejudice - a disposition to prejudge theists as bad because they are theists and give them no credit for goodness, not unlike the same types of attitudes we see in some towards other population subgroups.
Consistency would see both good and evil potentially motivated either by religion or our nature.
I go with the view that dispositions towards good and evil can be found in our nature. This, of course, creates problems for the popular thesis that we can answer the question, "What is good?" by looking at our nature. It also creates problems for those who claim to have proved that nature provides us a disposition to do good - who cannot, at the same time, give us a theory of "good" that our nature is supposed to be disposing us towards.
Religion is not to blame. No god was involved in the writing of scripture. Its contents and its interpretation do not come from an external divine source that we can blame for all of our problems. Religion comes from human beings and, actually, does a good job of reporting our nature. It tells us of the moral character of the people who wrote it - real human beings with human flaws that some people today treat as "all knowing" and "perfectly virtuous". Its interpretation tell us more about the person reading scripture than it does about the scripture itself.
There is no evil written into scripture that cannot also be written into an atheistic philosophy. Human beings who can write these evils into a religion can also write them into an atheist philosophy. Saying that "religion poisons everything" simply ignores the fact that the real fault - where religion is at fault - comes from the people who invented it and follow it. Those who can invent and follow a vile religious practice can invent and follow practices that do not mention a god.
We can see an example of this in Sam Harris' defense of torture.
We see evidence of this in Ayn Rand Objectivism, Communism, multiculturalism, social Darwinism, and other atheist philosophies.
Steven Weinberg said:
Religion is an insult to human dignity. With or without it you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion.
This is unvarnished bigotry, plain and simple. Atheists, too, can embrace philosophies with twisted concepts of what is right and wrong. When they do, then the charge mentioned above is just as applicable to that atheist as it is to any theists.
However, this fact does not appeal to those people who want the emotional satisfaction of seeing "us" atheists as morally superior to "them" theists. Weinberg's quote sooths our tribal prejudices - so it is embraced and promoted where it should be condemned.
Atheists have some work to do when it comes to morality. Converting people from theism to atheism simply is not sufficient.