Anessa overrrrreacts

Two weeks ago during an episode of Road Rules / Real World Challenge - The Duel, two of the participants had it off for "racist" motives.
Robin who was very drunk tells Anessa: "You are straight, gay, black, white, puerto rican, portuguese. Pick one!"
Anessa gets very upset with that comment and goes off on Robin, but instead of telling her why she thought she was wrong she keeps on kicking and screaming. Raving about such a racist comment.
I am also gay, but I could be straight, I am brazilian decendent from portuguese, italian, and who knows what else, maybe 1/10 black, 1/10 native brazilian and as far as I am concerned part of me could even be asian and I don't even know.
Anyway, why people care so much about races, colors and ethnicities in general in this country? Why every comment about race turns into a racist one?
I am sure it was an unfortunate and probably ignorant comment from Robin but give me a break. Just laugh about it.
My friend Cameron always says he is 1/4 chinese and no matter how many times he says it I laugh about it and make fun of him. Am I being racist?