Yes, of course, the group in power are the ones who benefit. Whether monetarily or psychologically.
In-group bias, people. Since we belong to a group, we have to believe that group is somehow superior to people outside the group, so we can feel good about ourselves. Yummy...You learn so many fun things in psych classes. It's almost like a cognitive disonance thing: since we're in this group, and we're better than average, this group must be better than average. And then that excuse is used to justify all kinds of things.
You should do some reading about the teacher who did a little eperiment in her classroom, where she seperated the kinds with blue eyes from everyone else, and said they were better. The kids actually started believing it, and acting as if they really were better. Then she switched, and said the blue eyes kids were worse, and everything switched as well. Crazy shit. I'll try to look up her name. Keep an eye out for an edit.
Works even when the seperating factor is something completely arbitrary, and there really IS no meaningful differences between the groups.
Edit:
Well, that was fast. Her name is Jane Elliot, here's a
link to the first page I came across.