As an example, the other night I was watching a special on the History channel called ‘Ancient Ink’ where some guy went around the world visiting tattoo artists who use techniques that are more or less ancient. Some of the comments were real gems, such as (paraphrased):

“Everywhere I traveled people were practicing ancient tattooing techniques” (to which I responded ‘Because those are the only places you went’)

“He’s using living flesh as a canvas” (”Yes, its a tattoo!”)

If people are constantly given comments like that that assume they’re stupid, they’re going to be lazy and stop trying to think and become stupid.