Can I chime in? This has happened to me before in a meeting at work. Anyway, I did a presentation of which my boss loved. Well, as everyone was leaving the conference room, this lady leaned over to her friend and said "I bet that black b*tch this she's hot stuff now?" while I had my back to them gathering my things. After hearing this, I turn around and said "Your MAMA!" and walked out! I know, that was totally childish but at that moment, I wasn't about to let her stupidity ruin my morning.
Good job sayin something back. I have no balls and I woulda just walked out but talked about it with other people. But I think in ur case that was a racial slur. You might see it different but I see that the same as sayin "I bet that *N* think she's hot stuff now". Maybe my interpretations are different. However, in that situation, it was not childish to yell "Your MAMA". I think that's quite funny