The idea behind this one, failing the false logic of "Omigod the Soviet Union," is that if socialism has never happened before it will never happen. "Name a society where your version of socialism has actually occurred," the debaters challenge me. This sort of challenge is supposed to be part of a proof that socialism is impossible. The people who argue this kind of stuff reason that there will always be some sort of ruling class, because some people (an elite few) were destined to rule while others (the great masses) were destined to follow. Socialism is, then, against human nature.
I suppose in one major sense this diary is a variation on a previous diary -- the "socialism is a utopian fantasy" diary. If socialism (at least of the conception discussed here, with public ownership and control over the means of production) has never happened before, this must be because it's impossible to enact, and so it's just a utopian fantasy. Right? Right? Never mind, of course, that social invention is still possible, and that the past may be no indicator whatsoever as to how the future will turn out.
(And of course if people had gotten to the Wright brothers and told them that nobody had yet found a way to make practical aircraft, they would still have invented an airplane, but only by ignoring what such people said.)