So what does that have to do with FDR?
The first part talks about the Federal Reserve. Which had nothing to do with FDR. He didn't create on it.
Since he didn't become president until 1933. 4 YEARS after the Crash of 1929.
Even then, he is speaking in conjecture. You can't prove that his policies made it worse. It's just this a belief.
Unless you can go back in time and change what happened to see a different outcome, it's all theory.
I understand the premise that he's making and it's very possible that it's correct, but we can't prove it.