Your friend, rather perversely I think, refers to the "disastrous results" that followed the monetary tightening of Volcker and other more monetarist-minded central bankers without even hinting at the facts that that the tightening was aimed at bringing down inflation rates, and that it succeeded remarkably well in doing precisely that. In other words, the tightening did precisely what monetarism said it would do, and what monetarists' critics at the time, wedded to the view that monetary policy was ineffective, and that inflation was entirely caused by OPEC (or by unions, or by anything except monetary policy) insisted it could not do. And yet your friend imagines that the experience proved the monetarists wrong!
George Selgin