Hello people :-) . I am a mixture of black white and a small bit of asian, so it's pretty much impossible for me to 'stick within my own race', and I am currently engaged to an awesome white guy. Personally I don't care in the slightest about colour, I've just only found white guys attractive so far? Does this make me racist? No. I just haven't met a black or south asian or east asian or mixed race guy yet that I've found attractive. Some things are and aren't supposed to be selective. Treating people nicely shouldn't be based on their colour. People shouldn't be denied jobs or opportunities based on their colour.
The thing with relationships is that they require more from you than just treating the person nicely; you have to actually love the person. So saying it's 'racist' to not like people with a certain look is bad because it encourages people to get into relationships with people that they don't actually care about in order to not seem 'racist', which is bad. Who you're attracted to is often based on the pheromones (scentless chemical signals) that they send off. People whose pheromones are complimentary to yours are the ones that you tend to like, so not liking certain people may be more genetic than decided.
Basically guys, being nice to everyone regardless of ethnicity/race is expected, being attracted to everyone is not because you can't control who you're attracted to. Simple as.