How did the Nazi Party rationalize the mass murder

The Nazi Party rationalized the mass murders through its well-invented propaganda. The massive propaganda was one of the most powerful sources that Nazis used to achieve their goals, so they used it frequently and on different ways.

One of its purpose was to justify the mass murders of Jewish people and their Allies. Nazis described Germany as a victim of Jewish aggression in order to justify their violence against innocent people. Hitler frequently stated that Jewish people and the Allies are spreading awful lies against Nazi Germany and their leadership.

The best example would be their invasion on Poland. Hitler invented Polish attack on a German radio station, under excuse that Germany was defending itself from Polish attacks. He actually tried to rationalize his invasion on Poland.