You could just as easily say that 'No one calls Mao Hitler' as well (though of course many do), as his horrors aren't given the same focus either.
What about Genghis Khan? His exploits killed a significant integer percentage of the entire human race! Yet he's more likely to be revered than compared to Hitler.
The presumption that only black mass murders are skipped over, then, is utter nonsense. Why some are focused on whilst other ignored (or in the case of Genghis, revered) is a mystery. And let us not forget that Genghis even killed white people, just like Hitler!