Expiry of food and bad attitude of manager

I ordered a chicken mushroom pot pie. It was sour and clearly past expiry. I informed our waiter who apologized for the food. I told him I would not order the same item again and I ordered a burger. Afterwards the manager approached us and I informed him off the situation. I told him I already ordered something else. This seemed to upset him, I also told him that the waiter informed me he was concerned about the food before serving us but was assured by kitchen staff it was prepared today. You could hear the manager was upset with the waiter but I could not hear what was exactly said. The manager came back to inform me that the kitchen staff added to many spices (the manager is determined not to admit fault or blame it on the staff who is obviously not in charge of buying stock). I said OK not feeling the need to further drag this out. I assume the waiter will lose his job or his wage to cover what is a mistake he made in the manager's opinion.Throughout this experience I would have never complained had it not been for the manager. He smiled and was polite but it felt insincere. Off course I hope the waiter is not punished for his actions since in my opinion he did everything right