As others have already mentioned, the idea that DMT affects people differently based on race is somewhat far fetched. That said, I could believe that, like other psychedelics, the effects will be different based on personal psychology, which is often (but not always) tied to the culture that you were immersed in while growing up (i.e. your family, etc).
OP: How do other psychedelic drugs (ex. mushrooms) affect you? Your post reminded me of another post that I saw a while ago where someone was tripping with his black friend who said something like, "black people aren't supposed to do this; these are white people drugs!" I LOLed at that. Once again, I can believe culturally-influenced psychology can have an effect, but I doubt there are any strictly racial differences.