I managed a gun counter for several years, typically with 10-16 people on staff at any given time. The staff was comprised mostly of just-out-of-high-school kids and old guys whose wives made them get a retirement job because they got too annoying around the house. I didn't find the young kids to be any more dumb/arrogant in their stupidity than the old guys generally. They do have more of a problem of hearing something one time from someone they like and taking it as gospel, which is really irritating. But on the flip side, I had a lot of the old guys who would go on and on about their marine/ army/ navy service to give them false credibility, only to go off on an ill-informed spiel about how terrible "plastic guns" are and how anything less than a .45 "will just -CENSORED--CENSORED--CENSORED--CENSORED- 'em off". They will talk about how cheep and useless ARs are compared to their A1, etc. The young guys can at least be taught- even if they're stubborn they tend to take in more information. A lot of the grandpa generation will not even consider any new information- they believe what they believe, whether or not it is based on fact. We also had a bit of an issue with 2 different older staff members who never thought twice about telling people to do something illegal. It really is not okay to tell someone how to turn their 10/22 full auto or the best place to spotlight deer without a game warden catching you.
I hired one guy, probably in his mid 60s. We'll call him "Jim", because that was his name. He'd been working at a gun range for years, he claimed to be a Glock armorer (though I once watched him struggle for several minutes to field strip one as he tried to push the nubby thing down on only one side. Also saw someone ask for a Glock 17 from the wall and watched him take down and read the slide on 3-4 different glocks before grabbing the 17. Our wall was organized by caliber, then brand, then full, compact, sub...), and he had a military background. He is the only person I ever fired, because he gave so much ridiculous misinformation to customers that many people ended up with guns that suited them horribly, based on some ugly old man's supposed personal experience.
While a lot of the kids on the counter had stupid opinions about some guns and accessories, I found that they nearly always had their facts right, or actually took the time to look them up if they didn't know an answer rather than pull something out of their butt to maintain the illusion.
I think the moral of the story is that people are dumb and impressionable as a species and it has little to do with age, and a lot more to do with how seriously the person takes their job and how willing they are to learn.