So, let's talk about the really basic case: calling people out for making racial slurs. If someone uses the n-word on my friend (or "faggot" or "jewed" or "gypped" or what have you), then me saying to that person, "Please don't say a mean, racist thing like that," fights against racism, by helping enforce a social norm that racism is not okay.

How would you recommend handling a situation like that? How would you work to stop a racist behavior, without making someone feel uncomfortable for doing it?