Let's face it, what good are dumb people if you can't laugh at them? Here's a few gems to get the ball rolling.
I am not in the least bit overweight or very old looking, but once I was enquiring as to the climbing efficiency of a certain 29er, and I was told, "Bikes don't matter, I could smoke you on my mountain bike with you on a road bike."
I asked about steel bead tires, and was told, "The hoop kind are kept downstairs."
More sad than funny, I was looking at another 29er (a $1400 bike) and was directed to a 450 dollar comfort bike.