Racism isn't funny.
No matter which way you look at it, joking about another pony's race is hurtful and mean; and us ponies definitely aren't about that. It is even hurtful to assume characteristics about a person based off of how they talk or where they're from. The Southern Poverty Law Center is a good resource to look into tracking and confronting hate of all types.
No matter what color your mane is, no matter what part of Equestria you're from and no matter what your neigh sounds like, the herd is a safe place for all bronies.
Melissa Harris Perry has a lot of feelings about Star Wars, primarily that it's racist, because Darth Vader was voiced by a black guy but played by a white guy.
The part where he was totally a black guy whose name was basically James Earl Jones...but while he was black he was terrible and bad and awful and used to cut off white men's hands, and didn't, you know, actually claim his son, but as soon as he claims his son and goes over to the good he takes off his mask and he's white.
Maybe she doesn't acknowledge the prequels as being real, and who can blame her for that, but Anakin/Vader is a white guy in those and he kills so many younglings. He also first "claims his son" while he's still "a black guy" (a whole movie before he takes off his mask) and, well, if you've ever heard Darth Vader's on-set voice, you'd understand why they dubbed over it with James Earl Jones: