No one has been forced to do anything.
Would it not be perfectly legal if McD charged $5 to take the cheese off?
Insane. Too many lawyers. They must have "lowered the bar."
In my mind, you are correct.
Fast food restaurants are food manufacturing companies. They have a set list of items they manufacture, e.g., Quarter Pounder with Cheese. Any deviation from that standard product is a custom order. Custom orders cost the manufacturer time and money when the process is deviated. In addition, McDonald's cash registers are item buttons and not regular cash registers.
The people ordered an item on the menu, got the item on the menu and they are still unhappy. If I ordered a Quarter Pounder with Cheese and expected Swiss Cheese, I would be the person with unrealistic expectations. They are similarly wrong in their expectations.