I posted a reply to another comment in this interesting blog about the promotion of the "free markets" concept in the 20th century.
Thanks for the bit about the tax reform of 1954.
But you could probably find rollbacks from the New Deal vision of Roosevelt as early as 1945. The one that stands out to me is the Taft Hartley act of 1947. I also wonder whether if FDR had lived longer, the Cold War could have been avoided and instead of the endless overt and covert wars we could have had the Four Freedoms. So another suspect is the National Security Act of 1947, which created the military industrial complex as we know it, and the endless pursuit of world control through military dominance.
These disgruntled aristocrats and petit bourgeois who started MPS were angry both at democracy and unions. Friedman blamed the business failures of his parents on unions.