We may believe in races and in ethnic groups as human differences which must be tolerated. We also categorize people we meet and know, in these kinds of 'labels', such as (apart from race) gender, religion, culture, age, sexual orientation, food habits, clothes style, etc.
All those things are the first characteristics we notice in someone when getting to know him or her. And as far as I am concerned, we prejudge and classify people without even knowing them, whatsoever they could bring to our lives, which seems to me really ignorant.
