I heard someone make a few arguments that I absolutely agree with:
1. If armed security guards are a bad idea in schools, which are targets, they should be a bad idea in airports, local/state/federal government property, outside the rich Beverly Hills home, and basically...armed private security guards should no longer exist.
2. If Joe citizen, who is also a target should not carry concealed, no one else other than law enforcement should either; including judges, private investigators, politicians, etc. Guns are bad, cops will arrive in a minute right?
3. The local business or rich guy should not be able to rent an off duty cop to protect them or their property just to get around who can carry a gun and protect said person or property. Guns are bad, on-duty cops are coming right?
There must be some gun restrictions, such as mental and criminal history, but other than that...leave lawful gun owners alone, and increase the public safety net for the mentally ill are the answers.