Looking at the arguments coming from the left with respect to the spectrum of liberal (classical) and authoritarian thinking is instructive. It helps put the historical fact that left-leaning governments always lean in the direction of authoritarianism into context.
Preference for state monopolies over free markets
Preference for central (government) control and planning over de-centralized, private collaboration
Coerced collectivism over individual liberty
Distrust of private ownership in areas of life and sectors of the economy
Attempts to restrict the expression of dissenting views (e.g. purging left-leaning online forums of non-left opinions, "shouting down" or attempts at disruption of public appearances by those with non-left opinions)
Instant application of odious labels to views deemed unacceptable (e.g. labeling those concerned about illegal immigration as racists)
A general hatred toward those who've become individually successful - attempts to paint individual success as incumbent on the exploitation of others