When I was 13 years old in 9th grade, I learned in debate class of the logical fallacy of Ad Hominem, which means "to/ against the man" in Latin. It means mouthing off about the kind of person your debate opponent is in an attempt to discredit his case rather than answering his argument.
I am 39 years old, and thru the years the # of times I have been right while an expert/ elder has been wrong is equal to the reverse.
This thread reminds me of when I was 23-25 y/o, recently grad. from University, and my father tried to force me to knuckle under by accusing me of 'thinking I knew everything' if I dared to disagree with him, even if the facts were on my side. Such behavior resulted eventually in my changing my last name legally.
IMO, it is ELDERS who tend to think they know everything. 'Because I'm older/ smarter/ more expert, I am automatically right,' & 'You're too young/dumb/rookie to know ANYTHING,' & 'I know best, therefore you are incompetent to run your own life,' are the HEART of know-it-all-ism.
By the logic of the poster above, anyone who sticks to his guns or refuses to be a sheep could be called a know-it-all. To believe that one knows SOMETHING that you don't is a far cry from believing that one knows EVERYTHING.
In contrast, when I am WRONG and someone else is RIGHT, I admit it gracefully, even if s/he is younger/ less expert/ of a lower IQ than myself.
In conclusion, please talk to each other lady/gentleman -to- lady/gentleman.