A lot of people are racist because of negative experience they have had with certain races.
For example I used to date this spanish chick who exclusively dates black men. Seriously if you arent black dont even look her way because she won't even acknowledge your presence. However, she has this complex about black women and has a bit of a attitude towards them. Now, this started because black women used to give her a hard time because she only dated black men. Now, I'm not saying shes right. Because in a way she is basing her negative attitude towards all black women because of the actions of a few but I understand shes only human and some people can't separate the two
Same can be said about black people that are racist as a result of their negative experiences with whites or other races.
I can honestly say I tend to have the same complex about people from New wYork. I always view them as rude, lacking manners and having that "superiority complex". Grwowing up in Miami i came accross a lot of those fukkas. So I tend to NOT always associate with them except for my fam and other friends. But damn near 75% of chicks I've dated are from there.