To summarize my main points about evil, the study and communicating about the behavior of groups of people requires that we be abstract. To translate the resulting understanding into action without hurting the subjects of that understanding, we must respect them as real people whose value is equivalent to that of the people we know directly, and as much as possible treat them as individuals. The alternative, identifying others as objects and acting accordingly, can easily cause harm – or worse.
Evil is not a characteristic of people, it is a characteristic of actions. People are capable of changing their behavior, and only in a limited way (through exploration), themselves. The seeds of evil are built into our genome; given the right circumstances, anyone can commit acts of evil. Therefore, people must be held accountable for what they do, not who they are.
Spirituality provides one way of limiting the evil people do, by instilling the basis of respect for others on an emotional level. But it can also have a negative effect, by allowing people to become too comfortable with their assumptions. Education and collective investigation (exemplified by science) can help, by providing a means of checking those assumptions and sharing the results, but it too has a down side: facilitating the development and dissemination of harmful technologies. Together, spirituality and science can be used to harness the positive power of abstraction, while limiting its great destructive power.