All so true. I'm mixed (Black father, white mother). I look white and encounter racists in my town often who feel completely free to spout their garbage to to or in my vicinity. When I tell them I'm mixed, I get either back-peddling or the rage that I've somehow trapped them to "make them look bad" (as if they needed me for that).
I used to be naive enough that I could, through my unique appearance and racial make up, educate and change minds. Ha! If only life were that simple.
Now I tell them purposely after letting them have enough rope to hang themselves. It sounds horrible to admit, but at this point, I quite like making them look as stupid as they are. If they get THAT angry, it's because somewhere, deep, deep down, they know they're wrong. They won't admit it. But I will admit it, their discomfort pleases me on some level. What they say and think doesn't change who I am.