We know the Nazis used German census data to identify Jews to round up. They also had many pseudo-scientific tests such as the size of a nose, to help them identify the Untermenschen in the general population. The next regime that pushes a superman theory will be able to base their selection criteria on DNA testing as soon as the perfect Nordic / Aryan genes are determined. Or pseudo determined. That's how you get from DNA testing to millions being killed or enslaved.