How to react when professor wrongly corrects you in public?

I recently defended my master thesis. One thing only went wrong: I said a certain method was rather new (which it was!) and the most senior professor in the room (my supervisor was not there, he had an unexpected meeting) contradicted me, telling me that it was old and had been done in the lab for ages.Honestly, I just gave in. He seemed so sure and I did not dare contradict him.However I was sure before and of course I have since checked, the method is indeed new, the professor was just plain wrong.What should I have done in the situation?