Imagining the Fed is controlled by the Primary Dealers is not a fundamental.
Two points. First, it's not "imagination". Second, it's very fundamental to the picture.
The Fed is simply a "pipeline" from the Primary Dealers to the U.S. government. The only thing that you could debate is the fact that a President "nominates" a Federal Reserve Board member once every even-numbered year to serve 14-year term. Past that, you're out of debating points.