So if everyone is walking around with a gun, there are no unarmed shootings and if there aren't any witnesses, all anyone (including police) has to do is say, "That person pointed their gun at me." So essentially, if you're packing, anyone else who is packing can shoot you and claim you pointed your gun at them. And if you're dead you can't argue it.
This will be especially helpful in Florida where they have 'stand your ground'. Killing unarmed people costs a lot in attorney fees and time to beat the rap but if someone is packing, ka-boom! "Hey, see that gun? He pointed it at me and I was in fear of losing my life." Sounds like an easy way to get rid of people who piss you off.