Movie: Intruder (1962)

You are an excellent manipulator. You know how to press on people's weaknesses. <...> You have an approach, a technique. But do you know what the problem is? You are too smart and there is no room for common sense in your head anymore. Because if you had it, you would realize that you started something that you cannot control. Do you think you're the boss now? Wake up guy, this mass is the boss now.