In the last 50 years I wonder how may cases exist where a person who was open carrying a handgun committed a violent crime? Seems that someone who was planning on committing a crime would conceal to avoid attracting attention to themselves.

If there is a tendency among gangbangers and other criminal types to open carry their handguns then LEOs zeroing in on people spotted open carrying is obviously justified. If criminal types typically do NOT open carry then at best there is a training problem.