While I didn't know him well, I did know that he had a temper and wasn't the sort of person that would stop talking or steer the conversation elsewhere. He'd argue his point until he was blue in the face, never yielding.
When arguing with a racist, your goal isn't to change their minds. That really doesn't work. It may have worked in the mid 1900's, when general ignorance was the cause of some racism, but not today.
Your goal is to make them look stupid. If they actually lose their temper, that's bonus points.
However, if you lose your temper yourself, or the type to get tongue-tied, just ignore them.