All I'm pointing out is it's a shitty argument with nothing of substance to back it up. People say it out of habit, but it doesn't lend it any more weight or authority than mere tradition grants to anything else.
I think the way communist states have all worked out (corrupt, collapse, or strong swings towards capitalism) is evidence. I think the general distaste for extremes is evidence.
Those things do happen to be evidence (potentially good, misleading, or basically useless evidence remains to be seen, but at least evidence), that quote is not evidence, it was given by someone who didn't even have the evidence you just mentioned, because it hadn't happened yet.
It's the equivalent of "Jesus said" or "Rush has been saying that for years!" It gets more scrutiny because of the effect it has when people believe it, just like Islam and Christianity get more scrutiny than Gnostic cults with 10 members.
If you're going to make the statement, at least use a good argument, is all I'm saying. That quote is something that was said by a person that had very little but personal opinion backing it up.