The major difference between Hitler and the Communist genocidal murderers -- Stalin, Mao and Pol Pot -- was what groups they chose for extermination.
For Hitler, first Jews and ultimately Slavs and other "non-Aryans" were declared the enemy and unworthy of life. For the Communists, the rich -- the bourgeoisie, land owners, and capitalists -- were labeled the enemy and regarded as unworthy of life.
Hitler mass-murdered on the basis of race, the Communists on the basis of class.
Because the Holocaust was unique in its industrialization of death and in its targeting of every Jew, including babies, for death, the post-World War II world has been rightly obsessed with eradicating racism (but not anti-Semitism!), i.e., the hatred of another solely because of race. But the world has not been obsessed with eradicating the other source of genocide: classism, or the hatred of others based on class.
The reason for this embrace is that class hatred is as fundamental to the left as the Trinity is to Christians, and the left dominates the media and education. This is dangerous because there is an ideological continuum from the democratic left to the Communist left. Making the rich into scapegoats for society's ills unites the left.
The democratic left believes in democracy, and, before the 1970s, some of its adherents were fierce anti-Communists. But while the decent and the indecent left differ on democracy versus tyranny and on non-violence versus violence, the nicest leftists in the world agree with the indecent left about who the enemy is.
Being on the left means that you divide the world between rich and poor much more than you divide it between good and evil. For the leftist, the existence of rich and poor -- (SET ITAL) inequality (END ITAL) -- is what constitutes evil. More than tyranny, inequality disturbs the left, including the non-Communist left. That is why so many on the left fell in love with Fidel Castro, Hugo Chavez and, at other times, with every left-wing dictator. Non-leftists see these men as thugs; much of the left sees them as fighters for equality. Yes, leftist dictators extinguish freedom and steal land and businesses from the rich -- but none of this disturbs most of the left.
In fact, the left sees left-wing dictators as kindred spirits in hating inequality. In 2009, nine left-wing Democratic congressmen, members of the Congressional Black Caucus, visited Fidel Castro in Cuba and came back awestruck by the dictator. They even refused to meet with one of Cuba's leading pro-democracy dissidents, Jorge Luis Garcia Perez, an African-Cuban.