I suppose Allies' propaganda called him that. For them, Czechoslovakia was Prague and nothing else. The Czechs knew he operated everywhere. Although he could certainly kill his mother for the greater good of Nazi Germany, he wasn't such a butcher there. He skillfully wiped out the fledgling Czech resistance (it wasn't that hard, early efforts were naive and amateurish everywhere) but simultaneously introduced many positive initiatives: free Saturdays, unemployment insurance, KdF, Labour Front, increased rations, wages and pensions (of course all that for the greater good of Nazi Germany). Generally, it seems many, especially the workers liked him there. This is why he traveled in an open top cabriolet with no security when they got him.