Many religions attempt to guide their followers toward an understanding of what is right and wrong. Flip to any page in the Bible and you can find a story that can be related to how you should treat others in your daily actions.
For many, morals are closely tied to religion. Many Americans fear those who do not share their religious beliefs because they might not share their morals. Consider the great amount of concern that was raised about John F. Kennedy being Roman Catholic in the run-up to his being elected president.
Atheists have long been feared for the same reason. If there is no Bible or religious text guiding their lives, do atheists really have any reason to act morally toward one another?
As an atheist, I can assure you that many do. Although many people equivocate religion and morality, each in fact represents a slightly different way of guiding the way that people should live.
Followers of a religion generally abide by the morals instructed by that religion because they either fear or love their God or gods: Don't steal or you'll go to hell.
At the same time, the morals that religion teaches frequently coincide with an empathetic or rational mindset: I won't steal because I don't think that would be fair to the person I would steal from. Atheists might not love or fear God, but many share an empathetic and rational mindset.
The morals of the atheist could in theory be very different from those of believers, but they usually are not. As it turns out, most of the teachings of the Bible that we still bother to follow are rationally defensible. There are certainly a few sticking points like the permissibility of abortion, but whether the Bible actually condemns abortion or not is up to the subjective interpretation of the reader. There are many theists who accept abortion and many atheists who oppose it.
In many ways, the laws of religious texts are much like the laws of man: neither is a perfect representation of what is moral or immoral. We can all find an immoral law, and we can all find an immoral religious teaching. Instead of using religion to delineate whether a certain group of people sharing a set of beliefs is moral or not, we should use reason.
Moreover, we need to be more accepting of one another's religious beliefs; our differences are not as noticeable as one might expect. Most atheists aren't godless communists seeking to destroy America. We are just like you.