I'm not exactly sure when it happened, but at some point in recent memory a couple of children I happen to know very, very well came to the conclusion that everything in this world is, I quote, "stupid."  Seriously, you can't talk about anything around them without them saying something like, "Yeah dinner was good, but yesterday at lunch Billy Bob said <fill in the blank>, and, you know, it was soo stuuupid." 

Essentially the tactic seems to be:

1. Identify something, anything, in the current conversation that can somehow be tangentially related to a conversation or observation that contained something easily identified as stupid.  Preferably that conversation or observation should involve a person who everyone just knows is stupid, but if that isn't an option then an episode of Family Guy is an acceptable substitute.  
2. Relate said conversation or observation in a style that takes twice as long as it needs to and contains approximately 42 uses of the word "like" and about half as many uses of the words "you know."
3. When parents or other adults don't reply with an appropriate level of laughter and instead look at you like, you know, you're stupid, simply think of another instance of recent stupidity and relate that one.
4. When the adult points out why something may not be stupid then look at the adult with an expression that says "In the near future you're going to be the subject of a stupid story." 

This really kind of bothered me until I remembered that they are 16 (almost 17) and 15 (almost 16), and that every human at that age seems to be possessed of incredible certitude without an ounce of wisdom.