In a wide range of media, people are not people. They are protagonists or antagonists, with the occasional bystander or anti-hero. They are not necessarily two dimensional characters, but they are still often placed into these roles, with inner conflicts and humanization subsumed by the unrelenting force of the plot. People seem to like this, it is simplicity in the whirlwind of confusion that is life. So this trend has been going on for quite some time. The majority of history, in fact. It is simple enough to work within the context of a story, where the author can make the character change as much as necessary to fit the image of virtue or sin. However, it extends far beyond what people might consider fiction, as it may be perceived in the context of religion, politics, and history. The way it works is simple: take a character (with all their conflicts, flaws, and little victories), and overlay onto that the idea of villain or hero, exaggerating any characteristics that fit the bill. In this way, these complex topics are narrowed down to good vs. evil. We use images such as light, dark, good, evil, purity, sin, etc., to make an us vs. them argument more convincing. We alter the truth, creating an image that far more people believe in, changing reality into fiction.
Essentially, the whole point of that messy blob of ideas up there is that images become more prevalent than reality because these images are more useful to us, no matter what side we are on. I don't believe there is any situation in which every single 'fact' points to the side of one argument. So...the world is post-modern only because images are more easily manipulated than people, so we have swapped over. The world is what we make it. Whoever this 'we' character is.