I don't open carry and I don't show my hand unless I'm fixing to shoot something. I don't think pulling a gun in a situation where you would be justified in shooting someone, but you don't should be a crime though. It's just that it's not something I would do. According to John Lott millions of crimes are deterred every year by merely showing a weapon.
It's a tricky situation for sure. I mean you really, REALLY don't "Want" to shoot someone if you can avoid it. But most of us won't pull a gun unless we have already decided to use it.
Scenario. You're walking to your car after a baseball game downtown with your 12 year old daughter. A guy armed with a big knife pops up in front of you and demands your money. You draw your weapon and are trained on him in 1.4 seconds flat. He puts his knife away, raises his hands and starts backing off. You gonna shoot him ? See, there could be exceptions, but generally speaking by the time you decide to draw your weapon you should have already decided to discharge it.