I shutdown, but am I being too sensitive?

I was in a car with my friend and a few homeless people we were helping (Organization work) and one of them started telling racist jokes ( I must mention I was the only black person in the car). I don't like racist jokes about anybody, so I put my headphones in to tune them out. Next thing you know my friend says "Did you hear the joke he said about black people?" And I said no, and she says "I'm glad you didn't hear that". Here I am thinking it is over, then she tells me the joke anyway seconds later, and I completely go silent. Lost my appetite. And that was honestly from a build-up of my pain/trauma being a form of amusement for her. She claims she only laughed because he was dumb enough to say it out loud. It wasn't so much the joke that offended me (ignorance doesn’t define me) , it was that she found entertainment in something meant to hurt me. Again.