Both atheists and theists of all faiths should recognize the fact that there is an important difference between being good and being religious. The main objective of religious practice is to develop a relationship with God, the All, the Absolute, or whatever you wish to call It. Religion, supposedly, provides the vehicle/s to do that through ritual, meditation, and prayer. A secondary goal of religion is to teach morality. Religion without morality is vacuous and useless. Religion with a corrupt morality (e.g. Aztecs) is dangerous.
What is morality?
In contrast to religion, the main objective of morality is to answer the question of how we deal with other people. Morality tries to teach such things as honesty, charity, integrity, love, character, and virtuous action. It has a much wider scope than religion alone, and it also gains input from at least two other sources: raw experience and philosophy. Because of this, there is such a thing as a moral atheist (I’ve met some). Likewise, there is such a thing as an immoral theist or even an immoral religion (again, the Aztecs come to mind).
However, most religious people are moral people. And most non-religious people, although perhaps not as dedicated to morality as the religious, are at least peaceful and non-violent. The problem for the non-religious is the despot like Stalin who comes to power and kills without conscience, answerable to no one but himself. The problem for the religious is a select number of zealots who kill in the name of their God as dictated by their corrupt religion. Although there are some benevolent zealots (e.g. Mother Theresa) most religious zealotry is undesirable. In modern times, Islamic Terrorists provide a dramatic example of religious zealots fighting on the side of evil.
Ultimately, the point to be understood from the above discussion is that, in a certain sense, morality is more important than mere religion. With respect to religion, humans will always be faced with a knowledge problem when dealing with God. Since we can’t even prove He exists, how can we possibly hope to prove we understand Him or His will? Morality, on the other hand, although not fully understood perhaps, can at least be addressed in human terms. We seem to recognize extremely evil acts and extraordinarily good acts with little difficulty. Coming to understand all the nitty-gritty details, however, is a lifelong process.
Ultimately, a world without religion would probably be quite dreary and empty, whereas a world without morality would inevitably self-destruct.