This is a common belief, but I've never seen any verifiable, credible evidence to support it.
With all due respect Frank, you're in California. And a citizen in one of the most liberal hot-beds in one of the most liberal states in the Union.
Also, note that we don't typically see any sort of surveys or polls in the national mainstream media about the concept of concealed vs. open carry either -- so how
would we come up with evidence to support that oft-mentioned notion about open carry?
I live in Washington, where open carry is.not only legal, it's... not uncommon. Even in Western Washington. Yeah, we've got the usual a$$hats in cammies or tactical clothing with thigh-drop holsters or cheap Uncle Mike's nylon rigs, the usual assortment of Wal-Mart denizens excercising their 2nd Amendment rights without a thought as to how they're really coming across to those fence-sitters who don't normally even think about people carrying firearms in public.
I will open carry while hiking in the Cascades, even in the national parks (Olympic, Mt Rainier), always when hunting and fishing, and especially east of the mountains in Central and Eastern Washington where folks don't stress about seeing firearms carried in public. In Seattle? Nope. T-town (Tacoma)? Nope. On the job? Yep.
But, given the preference, concealed is the way to go. Note to the OP: we discuss OC vs. CC a few times a year. You'll quickly deduce that most here are ardent believers in concealed carry. And no, seeing folks open-carrying is never gonna desensitize the soccer moms and skinny-jean-wearing man-bun dudes to the point where they won't freak out when they spot a gun on the guy in line at Starbucks.
As far as social norms, open carry may have been the norm in the 1870s and 1880s in the Western states, but I'd suggest it won't ever be the norm again anywhere in the USA (at least until after the zombie apocalypse begins).