The first amendment protects the freedom to peacefully assemble. In order to have a freedom, it is necessary to be able to execute that freedom in both the positive and the negative. For example, Freedom of Religon means that you are free to worship as you wish and the government can’t force you to worship something that you dont want to worship.
Freedom of Assembly is the same. You are free to both assemble for a purpose (say a Trump rally) and you are free to NOT assemble (say a Clinton rally) if you don’t want to. Conducting business is ONE of the reasons people assemble. It requires that both parties exercise their freedom (choice) to assemble. If either party does not wish to conduct business, they are free to not conduct business.
Private parties and individuals are free to not assemble if they do not want to. A private cake baker is free to accept WHOEVER they want as customers.
Every business transaction is a contract.
Is there any other contract that is considered valid when it is coerced?