SPEAKING TO ALL: Why do people choose to be racist?

I ask this because I see it a lot on here, well lol It doesn't really count on here, there's a lot of trolls, but also in real life. See I live in Texas, and lets just say some Texans still haven't let go of there racist up bringing. I have many friends sadly who have racist parents or grandparents and I even have a racist teacher. It can get to the point were I can't even hang out with some of them when I'm around their racist relatives, though some hide it and my teacher gives me attitude, ignores me when I ask her questions, gives me dirty looks, and does not help me when I struggle on work. Seriously throughout the school year I've always had to figure things out on my own in her cl, yet I still mange to make straight A's. I mean it's just ridiculous, to despise a person you barely know just because they are different from you? I mean dude, a lot of us are adults and young adults here, even teenagers should know that too. The worse part are STEREOTYPES, I could right a novel of stereotypes that are thrown against white, blacks, asians, indians, hispanic, etc, etc. When will people realize it is 2010, 2010 a brand new beautiful year, not 1890! We are a very diverse group of people on earth, so why do people choose to be racist because of it?