Uh, which progressives romanticize Hitler?! That's entirely a neo-Nazi thing, which is, as far as I've seen, 100% right-wing.

Anyway, conservatives do romanticize, say, Robert E. Lee, who after Jefferson Davis bears the largest responsibility for the 600kish deaths of the Civil War. (Yes, the North was the initial aggressor, but war is an appropriate response to stop things like genocide and mass enslavement.)

So again, I don't really see a major difference in kind here. There are some differences in degree, to be sure. And it is a more shocking contrast in progressives, whose smaller set of principles include those that were blatantly violated by people like Mao and Lenin--even though the (far) right has certain heroes who, curiously, trample on (some) key conservative/right-wing principles, when your list of principles is as short as approximately two, that your supposed hero is breaking them would seem to be a very important concern. But again, difference in degree, not in kind.