I suppose it depends whether you believe that 'evil' must have a motivation beyond human weakness & selfishness. I struggle with this idea most of the time, as its not exactly 'logical' to believe in the existence of some kind of 'Demon King'. Yet there are things that people do, individually & collectively, which seem in their effects, beyond the results of weakness & selfishness. I don't know whether its something 'internal' or 'external' to us, but its not part of our conscious selves. The desire to control, coerce, dominate, destroy, is in us, & can't always be traced to the effects of 'society' on us. You can look at all the economic & social reasons for the rise of Nazism, but none of that will explain the Holocaust.
Tolkien gives evil a mythological form in Middle Earth, & we get Morgoth & Sauron, but the 'effect' they have on Middle Earth is very much the kind of horrors we have witnessed in the past century - whether we can conclude from that that there is some kind of objectively existing 'evil' force behind events like the Somme & the Holocaust is one I can't answer - ask a theologian
