Did I act right or wrong in this situation? Racist attack towards my black friend.?

A couple of nights ago I was out with my friend (she's black, I'm white and were both brought up in London). We were outside a club which had just closed asking some people if there was anywhere else to go which was good. I don't know exactly how it started because I was talking to someone else, but I suddenly heard her shouting aggressively towards someone so I went over to see what was happening and she was having a fight with a young man (he was 24). I tried to pull her back, but she was really upset, so I pulled her back hard and calmly said to her "stay over there, calm down I'll talk to him" when I spoke to him he was very calm. But then my friend was angry at him for talking to me calmly because when she had gone up to him apparently he had said to her " F*** off you black bi**h, get back on the banana boat and float home to your own country". When she told me this (in front of him), I felt upset for her because no one should be spoken to like that, and she's also a very sweet and charming girl. So I started shouting at him too, just to let him know that I'm white and I don't think that's acceptable. Do you think I should of just made my friend walk away from the situation with me, or do you think it was better to defend her?