Its kind of like when the issue of gratuities comes up in the forums. A waiter or waitress will post a complaint that, generally speaking, people around these parts are poor tippers. Then everyone chimes in that they're excellent tippers giving their waiters exactly what they deserved and not a penny less.
Or when everyone claims their children are so well-behaved and they're great parents, when we all see bratty kids and bad parents in public?
Or when someone complains about sucky drivers, and everyone jumps in to insist that THEY are excellent drivers.