I'm going to agree with Scorp.

I once was mistaken for biracial. I don't really look it. My hair is dark, but my skin is pretty light even for part Caucasian, part Native American. As it happened, I was with an older black lady who was affectionatey called "Mom" by everyone who knew her. A man overheard me calling her Mom, thought she really was my mother, and was pretty rude to me as a result.

Your post is the same as if I had gotten angry and responded, "What are you talking about? I'm not a...." and then used a racial slur.