That which is good ultimately prevails as the entire structure inevitably collapses.  Evil is
always the victim of evil due, in part, attributable to the finite nature of its expression.  Evil is
restricted to the planet earth and a vision of the moment while that which is good can petition
a collective humanity and the legacies of noble predecessors.
Perhaps it is the case that a distorted free-will can be harnessed to serve the
purpose of evil.  The leaders of any given evil ideology initiate the process by
choosing and/or creating a framework made most appealing by the premier
principle being 'service to self'.
The act of intentionally causing harm to innocents cannot be subject to any
rational explanation.  A choice has been made and it is the decision to
comply with the assigned tasks necessary for full implementation of the evil
ideology in question.  There are no mitigating circumstances or legitimate
comparisons to suggest such actions could ever be considered a lesser evil.
Perpetration of evil ideology requires both a pervasive complicity and the
expenditure of considerable effort.  At some point all involved in the
perpetration of evil acts arrive at a point where a conscious decision to
participate is made.  A significant number of the guilty would argue their
actions had nothing to do with personal choice; claiming obligations to family
and/or mandatory compliance with orders..  
Any review of history reveals that the works of 'true-evil' often include atrocities
beyond the ability of any individual to comprehend.  It is in the beholding of the
past and present existence of true evil where the notion of a benevolent Creator
experiences its greatest challenge
But.... then again, and Meanwhile...
Is it possible that the acquisition of free-will can be directed to the service of 'evil'?
Implementation is the next step...
Throughout the entire process free-will is continually exercised soon to merge  
with intent as a greater society becomes more reflective of a desperate and
demented ideology.