If someone is not nice to you, laugh it off and take it as if
  its a joke. They can walk away happy (that they 'got one over on
  you') and you don't get your ego bruised. If you decide to
  'defend your honor' (how dare they treat me like i'm stupid!),
  then you've just lowered yourself and fallen into the trap.
  Change the rules of the game by not playing the same game.
  You're playing a different game. (along the lines of ''I'm
  rubber, you're glue. Whatever you say bounces off me and sticks
  to you')