Very similar to what fascists do whenever they take over.
They dictate prices for goods and services,
then dictate that providers MUST provide at that price or face penalties.
Slavery.
Carter dictated prices of gas when he was in office. It led to rationing. You take the free market controls away and there has to be a way to control demand. In this case you will have to control supply by mandating that doctors accept medicare at a loss. What do they do when doctors quit and there aren’t enough new doctors to replace them?