I maight be wrong, but I tend to favor the CFI, he has a lot more experience than the student, in the airplane and aeronautical knowledge, and if he put his thumb on the controls, I think he had a valid reason. Now, if he does it again on your next landing, you are doing something wrong that he needs to teach you about; If he doesn't teach you anything, then I would say he doesn't feel comfortable in the airplane, or as a CFI. Then maybe you should consider looking for another one.
You will see when (if) you ever become a CFI, the students will teach you maneuvers that you didn't think were possible!! Could be interresting!!