The idea behind "open carry" (at least the publicly legitimizing idea) is that an armed society is a polite (and thus safe) society, and if people are carrying firearms openly, the Bad Guys won't start any trouble.
Which sounds good, until you end up with a case where an openly carrying person was the Bad Guy, the open carry was a sign the guy was an impending thread, and 911 declined to do anything about it because it was legal.
Is that enough to change the policy? Maybe not. But it's worth some consideration.
In Colorado Springs, dispatcher brushed off reports of a man with a gun, witness says
“She said, you know, we have that law here.” Open carry is legal. “And it just kind of blew me away.”
The 'armed society is a polite society' concept is predicated on deterrence. If someone is actually suicidal, then it's very easy to get into an amplified response, where suicidal person pulls out a gun and starts shooting, other people pull out guns and start shooting because of suicidal person, more people yet pull out guns and start shooting in self-defense, and you end up with something like the bar shootout in Waco.
I’m less concerned about actively suicidal, and more so about simply stupid. Person X decides that Person Y is [bad, a shoplifter, black, white, christian, muslim, somehow a threat] and pulls a gun. Even easier if person X has been drinking, but it’s still early days.
For a dispatcher to decide that someone might legally be carrying instead of sending someone to check it out is criminal negligence. So is not having a weapon properly secured so that it falls out of it’s holster and accidentally discharges.