A few lines of wisdom from Slavoj Žižek’s Living in the End Times:

[I]t is not enough to say that the idea of Communism should not be applied as an abstract dogma, that, in each case, concrete circumstances should be taken into consideration.  It is also not enough to say, apropos the fiasco of the twentieth-century Communist countries, that this mis-application in no way disqualifies the idea of Communism.  The idea’s imperfect [or, rather, catastrophic] actualizations bear witness to an “inner contradiction” at the very heart of the idea.)  (pg. 20)

As Žižek notes earlier, one must also dispel the notion that Stalin was merely a clever, cynical manipulator:

This brings us to the limit of liberal interpretations of Stalinism, which becomes palpable when liberal critics tackle the motivations of the Stalinist: they dismiss Stalinist ideology as a mere cynical and deceptive mask, and locate beneath it a brutal, egotistic individual who cares only about power and pleasure. In this way the “pre-ideological” utilitarian individual is posited as the true figure beneath the ideological mask.  The presupposition is here that the Stalinist subject related in a purely external-instrumental way towards his language, disposing of another code (the pre-ideological utilitarian one) which enabled him to be fully aware of his true motivations.  But, what if — cynical though the Stalinists’ use of official jargon was — they did not dispose of any such alternative language to articulate their truth?  Is it not this properly Stalinist madness which is obliterated by the liberal critics, ensuring that we remain safely moored in the commonsense image of a human being?  (pg. 7)