The law, in my not so humble opinion is being fair here.
Now, if I run a place of business with a parking lot, do I want the cost for the maintenance of additional private security to demonstrate to a potential court that I took measures to protect the unarmed from an armed nutjob?
No.
Do I want the cost of liability for not having broken up an armed dispute on my property?
No.
Do I want the deep-pocket liability for secondary damages caused by stolen weapons taken from a parked car on my lot?
No.
Do I want the cost of adding additional fencing, etc. to preclude such an event? What if I'm just a mom and pop shop?
Now, mind you, these few I just dreamed up in a couple of minutes. The point is, there are issues in this tension between a private landowner and the owner of a weapon desiring to leave it in his car. Frankly, as a business owner, I'd feel safer if he carried it into the building and checked it at the door. Wouldn't you? But then, how would you feel handing a loaded weapon to a guy you just fired?
If not, your input is most welcome.