It's the effect of people being conditioned over generations to reject the "good". Fundamentally, things that work and are stable can be seen as true and morality is supposed to initiate enough people into following something vaguely approximating that abstract concept for society to function. You don't have to conceive of it in a religious way but that's what people mean when they talk about the battle of good and evil. There are always a minority who very consciously follow evil but they are now powerful enough to let their mask slip as those in the middle are now too ignorant to recognise the danger or are gradually being led that way themselves.