To be honest, I think labelling any film as 'evil' is simplistic and extremely provocative. Even something like The Triumph of the Will (a superb cinematic achievement) would struggle to meet that description and, though Birth of a Nation has some morally repugnant politics, I wouldn't label it as 'evil' either.
In terms of content (this really should the one for the 'most offensive film to 'thread), the one which comes closest is
Der ewige Jude, a vile 'documentary' designed to stir of anti-Semitism in Nazi Germany. However, because it is so obviously an anti-Semitic work of propaganda, I found the period drama
Jud Süß (another German propaganda film from 1940) to be more sinister, disturbing and devious. (Its director, Veit Harlan, stood trial for crimes against humanity.)
By way of explanation, I don't set out to watch Nazi anti-Semitic films – these two were part of a module I did as University on German cinema.
