I usually turn the table on them and just start out with calling 'em fascists. The look of puzzlement on their face is worth it.

But it's the liberal way actually. When the Nazi party calls themselves socialists, and their writings and philosophies proved it, it made things difficult for the fellow travelers in the academic ranks. So they simply started the lie that Nazi's are right wing... and repeat it over and over and over again to students who treat it as gospel. That's how the new truth is disseminated to the population.