THERE'S NO SCALE LARGE ENOUGH: Measuring left-wing authoritarianism in America.

...a more fundamental definition of authoritarianism would be: The belief that one’s values are superior to the values of others and that one’s beliefs can therefore be ethically imposed upon those with inferior morals.

Not to claim that conservatives are guilt-free, but that definition is as precise a one as I have ever seen of the progressive/liberal mindset.