Now I was going to flood the rest of this blog with research and sources. You know what I will share my own experience instead.
Growing up in Spain as a half American and half Spanish I was bullied quite a bit, now I don't hold it against the country as a whole, I had some decent friends growing up. The truth is discrimination in general just might be a natural feeling just as anger, happiness or annoyance. Just like those natural feelings it has to develop to be channeled appropriately. In a functional family the parents normally would raise the children and teach them how to channel their emotions in a functional manner. Discrimination seems to be the one that we forget about.
Racism is actually a relatively recent form of discrimination. Race as we know it today wasn't even a label for humans until the 19th century. Scientifically we are all the same race no matter the color of your skin. Before the 19th century discrimination didn't really have anything to do with race as we know it today. Discrimination had more to do with where you were from and if you were from a society that has been conquered or not. For example when the Roman Empire conquered Gaul (now known as Northern Europe) the inhabitants were discriminated against and enslaved to Roman citizens. Even within the Rome discrimination was also applicable to class, and if you were the lowest of the classes you would be treated like crap and possibly also enslaved regardless of the color of your skin. So what happened at the turn of the 19th century that discrimination took a new form of racism?