Smearing the (political) enemy with moral pejoratives has an old tradition. If you do it often enough some of the slur may actually stick. As it frequently does
The hatred of the Russians for the Nazis is a good example.
National Socialism and Communism are kindred ideologies. But Hitler stabbed Stalin in the back after the Molotov-Von Ribbentrop Pact, and ever since every Russian enemy is called a 'Nazi'.