Mengele conducted medical experiments on twins. He also directed serological experiments on Roma (Gypsies), as did Werner Fischer at Sachsenhausen, in order to determine how different "races" withstood various contagious diseases. The research of August Hirt at Strasbourg University also intended to establish "Jewish racial inferiority."
There is no ethical thing about this "Jewish racial inferiority" because with the resilience of some races to different diseases, they established the "inferiority" at where they were researching. It causes problems because it makes it cloudy to the minds if they were helping or not.