This would only refute his claim if the history of America began in something like 1964! American political history and even the history of the word, "Liberalism" versus the word "liberalism" is far more complicated, dynamic and dialectical than either of you seem willing to admit or consider.
A good place to start to disentangle some of your seeming misunderstandings might be Domenico Losurdo's Liberalism: A Counter-History (2011) from my favorite left publisher Verso.
For Marxists here are two recent additions:
Terry Eagleton: Why Marx Was Right (2011)
Eric Hobsbaum's last book: How To Change The World: Reflections on Marx and Marxism (2011)
Both from Yale University Press
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