I can top that, Chaser, in the stupidity category, which you know so much of and I rarely venture...
One time, I was riding the elevator at Delta where I worked as a network admin/field service tech, and this guy got on. He looked at me, I looked at him, and I noticed he had something on his forehead. I said, "Excuse me. You have something on your forehead." He just rolls his eyes at me and doesn't say another word and doesn't look at me again. I thought, "How rude!" Then when I got home, I told my husband about this, because I thought the guy looked ridiculous, and I was only trying to do him a favor, and he was rude, so it bothered me, and my Catholic hubby tells me, "It's Lent, you dummy!" I'm like, "What's lent?"