I see this alot outside and in school from every race,especially white (not tryint to be offensive or anything). But I cant tell you how many times someone called me "mexican" i dont go up to people and say hey your african, or hey your skin turns red in sunlight. It happens almost everyday and i laugh cuz they're ignorant and stupid.
Congratz on 5000 posts btw... but on to the topic. I see that alot to but it's just one of those thing you just have to learn to deal with especially living in america. Racism may not be as bad as it used to...and alot of time it's not even used in an attempt to hurt someone, it's just a generalization(sp?) that ignorant people use to describe someone or something that they don't understand. I'm not promoting racism or anything but If I were you I would ask them if they are british, or african, chinese..etc depending on the purpose...and eventually maybe some of them will stop doing it.