30 fps vs. 60fps: Am I crazy for not seeing a difference?

The only time someone has ever insulted me for my beliefs was when I claimed that I could honestly not see the difference between 30fps and 60fps. Now, either I am lying, you are lying, or neither of us is lying. Could it be possible that, just like colour blindness, some people are just incapable of seeing a difference? I am asking now in the hopes that the discussion remains civil