Why Are People Stupid?

Lots of times I feel like there should be a basic IQ test before someone in WoW can be allowed into groups. Lately, when I've been trying to get groups people tend to make the mistake in thinking I'm a healer. Even when I put SHADOW! in my note! This one guy, after we had the group all ready (or so we though), said "Okay, Eve, so you're healing?" I slapped my forehead and said "No. I told you I was shadow..." To this the idiot replied, "So you crit heal?" That's when I left the party. I don't know how this happens. I don't know how people mistake shadow for healers, or fury or arms warriors for tanks, or anything else like that. They are so completely opposite that I once assumed people knew the difference. Well, now I know to put the words shadow and DPS in my note. If they get messed up with even that, then god help them. I think maybe the problem is that they just see priest and say "yeeehaw, we gots ourselveses a healerz!" No! Bad! If you're one of these people, please learn the difference so that I don't have to gank you with my ally!