If anyone else thinks that Mike has proved me wrong here, please clue me in. I don't see it. Unless he'd like to split hairs between "stupid" and "dumb" (they are listed as synonyms however, so that would be a pretty thin case).
Chris, I don't see where Mike said that your teacher was dumb. He said that your statement implies that your teacher is dumb. He wasn't critiquing your teacher, but your statement:
""Pooh. What you're saying implies that Mochizuki was too dumb to realize that you didn't get it."