Convincing Insults?

There was this time, in my long gone childhood, when I had a rooted conviction that 2+2 equaled 5. At that time, between my father and my math teacher, I probably learned every possible synonym that could be used to call someone mentally deficient. After being so insulted I eventually conceded that 2+2 may well be equal to 4 after all. I believe that there are countries in the world today