The homo sapien species?

Which of these are more genetically beneficial for our entire Homo Sapien Sapiens species?

• I know this is long but please bear with me. I'm asking this question because I hear a lot of racist people like White supremacists who know jack about the science of genetics say that ethnic heterogenity with inter-racial couples that produce multi-ethnic children is dangerous to any particular "race" (I put quotes on this word because it's a contraversial term that credible anthropologists abandoned long ago). Those racist people believe that ethnic homogenity ensures the survival of their "race" and (for racists who believe anyone outside their own ethnic group is not human) save humanity from extinction. As I said, these racist people know jack about genetics and they go around spreading their "White superiority" psuedo-science to the public much like creationists do with creationism. I want to hear answers from people are more better-versed in this subject. Is it more genetically advantageous if people of various ethnic groups: - remain ethnically homogenous? - or is it genetically better if members of our own species of various ethnic groups mix n' match and create mult-ethnic children (ALL at their own free will)? Correct me if I'm wrong but, I think ethnic heterogenity is more favorable to the survival of our species as a whole because, as it allows greater gene flow among populations, it allows the flow of useful genes that are present in one ethnic group, or population, to another that lacks those traits. I'm talking about useful genes like the genes for sickle-cell anemia (common among African populations) which is useful against fighting malaria. Or genes that allow people to survive with lower oxygen consumption at higher altitudes (common among people in the Himalayas). I think if ethnic groups remain homogenous long enough, eventually as we progress in our evolutionary path, humanity will divide up and diverge into sub-species where we are no longer able to interbreed together and we will be pitted against each other to compete for survival

• Answer:

  genetic variation and mixing is better. "Purity" is just a fancy word for in-breeding. All pure-breed dogs have serious health problems, and are less able to survive than mixed breeds.