Again, not arguing that targeting others is better than your own people, but to the Nazis, the Jews were not Germans. Does that make it right? No because you shouldn't murder anyone. To Hitler however, Germany was being strengthened by wiping out these people, while Stalin's murders were mostly attempts to cover his own ass. Hitler of course had political opponents killed as well but it never reached the extent of the Great Purge. Its hard to say if this makes Stalin more cruel, but I definitly think his murders were more personal in nature.