Case in point; we went out to lunch yesterday. David, my five year old, had to go to the bathroom. While he was sitting in the stall, he start looking at the graffiti on the walls around them; he can read a little, but thankfully not a lot yet.
"What does this say, Daddy?" he asked.
"You don't want to know, " I said, "people write filthy words in bathroom stalls."
"Why do people do that?"
"I don't know," I said, "I've never had the urge, myself."
He thought for a second, then said "Maybe it's because people do filthy things in here."
The more I think about it, the more I think he's right.