Evolution is all about acceptance. Can you accept that humans evolved from apes? Can you accept that all life has evolved from simple single cell organisms and that there was no "magic" involved. Just millions and millions of years, mutation and survival of the fittest.
Some people refuse to accept that humans aren't special. That we have no special divine purpose and that the world and all in it wasn't created for us. That the entire human history is only a short parenthesis in the history of the planet...It's understandable because if one major thing is false in their belief system it likely means that everything could be false including eternal life and whatever "rewards" they expect.
It's more the fear of having their entire world rocked than that they are mentally retarded I would guess. Because at this stage you cannot deny evolution. Evidence is all over and even in your own body. So yeah it's a bit like saying the earth is flat or that the sun rotates around the earth. Still a flat-earth-society exists. So I mean it's not like we can expect creationists to disappear...
Good points, especially the bit about evolution being about acceptance. You can't say you "believe in evolution", you either accept a fact or you don't, but you can't believe in a fact like you believe in, say, ghosts.