It's really not, when you really go down into the actual numbers. Are the differences significant? yes, do they matter? most likely not. Because even if they are significant, it says nothing about their magnitude, just the likelihood that they are caused by the independent variable.
What this means is, sure, there are genetic differences that correlate significantly with common social categories of race (scientists use ethnicity, because of eugenics), due to continental size selection pressure, which is very broad and non-specific. However, this brush is actually so broad that it doesn't contraindicate common treatment at all. An individual person could or could not be hypersensitive to nonsteroidal anti-inflammatory drugs, for example. This has been found to have some pharmacogenetic correlation with some ethnicities. But if you were to alter treatment to one ethnicity assuming that they are more likely to have this genetic difference, you would lose far more patients than you would save. Because the correlation exists, it is significant, but it's magnitude is not very large. Instead, we have individual tests that are far more straight forward and will tell you with higher degree of certainty than ethnicity whether someone has or does not have NSAID sensitivity. There's also no basis to decide to whom to apply this test, based on ethnicity, either. Because all and any ethnicity can have NSAID hypersensitivity. So, we just do the test to everyone and every single patient gets the question “are you allergic to any drug?” regardless of ethnicity, doctors just don't think about ethnicity all that much if they are doing evidence based medicine and are not blatant eugenic racists. That's is how useless of an analysis category race is in science. Genetically speaking, large masses of people are actually not that different from each other that it grants much differential treatment. You rather treat the individual.