Take the time to dig into vicious acts, whether by an individual (Think: mass murders) or group (Think: genocide such as the holocaust), and you’ll come to the choices made by either individuals or groups. The genocide in Darfur and the South Sudan are the result of the choices made by the “soldiers” committing the murders. They have chosen to put their understanding of their religion and its edicts ahead of generosity, compassion and acceptance of the rights of individuals to worship God in their own way. That’s selfish. Very selfish.
A Corollary: Satan (or any other name you choose to give evil) is the personification of evil and is not real. Dig deep enough in any situation where you were thwarted in pursuing a good objective and I bet you will find the selfish acts of someone or some group. We don’t always have the time or “want-to” to dig far enough and consequently assign the barriers to “Evil”. Is it really necessary to get to the bottom of the issue? Well, not really. Just chalk it up to “Someone is being selfish”, look for a path around the barrier and get on with your project.
That said, we need to examine our own wants and desires to evaluate whether we are being selfish or reasonably taking care of ourselves. Key question being: Am I hurting or depriving someone to gain the goal I seek? (Contact sports excluded, except for “hits after the whistle” and other unnecessary roughness.) But I’m probably preaching to the choir here, since I suspect that sociopaths don’t read philosophical treatises.