Well, not sure about the good/evil thing, but whoever thought that they should make backgrounds white to be like books (at least that's the main reason I've heard), was totally off. There is a difference between reflected and emitted light.
With a reflective reading source, you can change the brightness by small changes in the angle you hold the reading material, but the biggest problem, in order to get more contrast, you can't go any darker than applying 0%, so the only way to get more contrast is to raise the top end of the scale (i.e. make it brighter).
For movies/TV this isn't so bad, but for reading text, how many of you shine a flashlight in your eyes and block letter shaped shadows to create text? The source of the light with an emitting source is the one shining into your eyes!
If you have any cloudiness in your eye, dirty contact, or a past eye infection or lasik that can leave invisible scars when the surgery is performed, but show up as slight cloudy areas years later as your eye ages. Or, if you just came back from swimming and have chlorine-eyes. any Bright areas will bleed out over dark areas -- making text harder to read and low-light areas masked by the light bleed over those areas.
I'm surprised that black on white became so popular/common -- if it wasn't backlit, it would be fine, but most computer screens are backlit. Seeing lighter text on a dark background is so much easier for your eyes to focus on. There's also a difference where your eyes tend to focus with different color and different brightness text. With bright text on dark background, your eyes focus on the characters, exactly. But with black text on white background, your eye will focus just slightly in front of the text!
Yeah, your eye focuses on brighter objects, as they stimulate your eye's receptor cells. This means the black text will always be a bit less in focus and your eye has to work harder to bring it into focus -- thus the common symptom of staring at monitors causing eye fatigue in many people. Since your eye has to over focus, the muscles in the eye are constantly active - because you are trying to overcome the natural tendency to focus on the bright object (the background).
Since the muscles in the eye are used to read up-close material (to make the eye lens thicker, to increase its magnification -- like shape of a magnifying glass vs. flat glass that provides no magnification). Over time, the muscles become shortened and they eye starts to distort -- meaning you can't relax the eye to turn off or remove magnification when you want to look at things far away. This chronic flexing of the eye for close work, is thought to be one of the largest causes of nearsightedness or myopia, increasing with age. Reading dark text on a bright field will unnecessarily and prematurely age the eye.
This will be most noted with those who spend time in browsers trying to make screen text look like book text.
Unfortunately, its difficult to find well designed User-Interfaces. While UI-studies were commonplace in the 60's and 70's as computer vendors spent a fair amount of time in trying to make the computer interface easier for people to use. Now that computers are necessarily, UI studies are gone -- it is assumed that people will be adapted to the computers. Instead of well designed tools to make our life easier, we are being adjusted to be better tools for the computer.
BTW, as far as qualifications to speak about computers and user interfaces, my University major was in Computer Science from the engineering college. I also had an emphasis in operating systems and user interfaces at the school that created the first generation of the internet, ARPANET, its first popular web browser, Mosaic (developed at the University's National Center for Supercomputing Applications (NCSA) at the U. of Illinois in Urbana, Illinois).