We don't???
We have some, many more have been struke down by the courts. The Supreme Court no longer makes a run for the border when a law that may be racist, or applied in a racist manner is challenged and appealed to them. The situations aren't even really comparable. Other than for in the context of voting, sexism and racism are not explictly prohibited by the Constitution. Infringing on the right of people to keep and bear arms is. The challenges to racist and sexist laws come via the "equal protection" clause of the 14th amendment, other than voting rights cases.