I should point out, groups like this don't really occur in nature, unless the people involved are VERY brainwashed by multiculturalism.
In my experience (in a very racially diverse public high school), the different genders and races all sat at different tables and socialized with members of their own race.
Self-imposed segregation, if you will. I guess it's natural to feel comfortable around people who are somewhat like yourself. Why not?
Read the Bible -- it explicitly states that "economic discrimination" is ok. It speaks about how rich men and poor men should not be buddies, because one will use the other, etc.
Here is the quote: (Ecclesiasticus 13)
2 He shall take a burden upon him that hath fellowship with one more honourable than himself. And have no fellowship with one that is richer than thyself. 3 What agreement shall the earthen pot have with the kettle? for if they knock one against the other, it shall be broken. 4 The rich man hath done wrong, and yet he will fume: but the poor is wronged and must hold his peace. 5 If thou give, he will make use of thee: and if thou have nothing, he will forsake thee.
6 If thou have any thing, he will live with thee, and will make thee bare, and he will not be sorry for thee. 7 If he have need of thee he will deceive thee, and smiling upon thee will put thee in hope; he will speak thee fair, and will say: What wantest thou?