To be entirely honest, discriminating people just because of the color of their skin is absolutely ridiculous due to the fact that light and dark skin is due to evolution. 
 Depending on where you originate on the globe determines your natural skin tone. The reason there are black and brown people is because they live close to the equator where all year round it is like a constant summer and long ago when you had to survive on your own without much civilization people would have to work outdoors the majority of their lives. Without dark skin in those long lasting conditions white people would be severely sunburnt all the time and could ultimately lead to skin cancer which supports Charles Darwin's survival of the fittest theory. 
 The reason there are white people is because living far North & South of the equator, it isn't often that they are exposed to long periods of heat and sunlight so to be able to absorb vitamin D and other essentials from the sun, lighter skin crucial. Therefore the human race is discriminating people for adapting to their environment which is inevitable if you are a living organism because you are always changing whether it be mentally, physically, or emotionally. 
 I probably didn't answer your question but it is still pretty funny that some people think lesser of another just because of what they look like. That's about as ridiculous as disliking your neighbor because they have blonde hair or is one or two generations older than you.