Eureka! I think I have sussed out what the dreaded "Q" word is: "Quiet!"
DUmmies hate to be told to be quiet because first of all, many times they don't even realize they are talking out loud, they think they are thinking it in their heads. Terribly embarrassing.
Secondly, they think they are so full of right knowledge that they have the right to never shut up.
If "Get over yourself" was a word, that would be the G word.