Let's not make the anti-'s arguments for them...
“You mean like the bank guards?”
Of which haven’t been much of a deterrent. Knowing who is carrying makes for management of those persons. NOT knowing who is carrying makes for a big unknown and that spells risk. This is why gun crimes goes down in areas with new concealed laws: The criminals get nervous.
Remember, we said “tactical” advantage, not “strategic”. While the bad guys are worried about those with guns strapped to their hip, they arent paying me and my concealed weapon much of a bother.
So you’re hoping the robber makes a judgment call about the number of people openly packing before they arrive. If they made judgment calls in the first place, they wouldn’t be robbing banks.