Communication with teenagers

David: I've been pondering..
Me: hmm?
David: Have you ever noticed how frisbees get larger the longer you look at them? then it hit me.. oh.. see that boy over there *points to boy leaving karate* he's only 11 and he's got a brown belt.
Me: Well, maybe he should wash it then.
David: ...
Me: see how I made it sound like his belt was brown because it was dirty?
David: You say the most ridiculous things, I'm not going to talk to you _any_more_