Azir Nafisi and the Root of Evil

Azir Nafisi wrote in her book Reading Lolita in Tehran that the best and worst among us can be evil since evil is nothing more than the inability or unwillingness to see or empathize with those around us. Evil then is the lack of understanding, conscious or unconscious, in regards to the viewpoints of and concerns of others. A corollary to this lack of empathy is a willingness to force ideas or choices upon others. This stems from the perceived inability of the "evil" person to sense why these actions may be inappropriate.
But somehow this seems to simplistic. Is the root of all evil really the the lack of empathy? Was Adolf Hitler's first and most damning crime an inability to to sense, or a disregard for, the lives, hopes and dreams of the millions that he sent to their deaths? Were his further crimes merely an extension of this inability to sense the hurt and damage around him, this lack of empathy leading him to force others down the path of his choosing? If this is true how do we explain the millions of German citizens who willing went where he led?
There is a part of me that wants to revile the evildoer, hate them and believe that their choices were conscious, and consciously inflicted upon their victims. It seems too neat to ascribe their actions to what is essentially self-interest. This is essentially admitting that the "evil" person is more willing to disregard the causes and effects of their actions as they move through the world, casting people out of their way.