Was my brother right in cutting off our parents for being racist?

My brother and I are very close. He recently decided to cut off our parents after they made racist comments towards his black girlfriend. We all met her and despite the fact that she is beautiful, successful, intelligent and makes my brother happy, my parents still told him to go date a white girl. I was very offended too. My brother confronted our parents and they refused to apologize and are now even accused his girlfriend of manipulating him into calling his family racist. They want him to keep in touch with them, but refuse to stop acting like racist bigots. My mother is constantly begging me to try to convince him to break up with his girl, but I personally support his decision. What's the best way to cope with racist parents who just won't get it?