We have hashed this "Private Property" debate sooo many times, I wrote this short response in the case it ever came up again.
You get to say what goes on, with your property, up until the time you open it up to business with the general public.
At that moment, you lose much of what you thought you had a right to.
Just about every aspect of your business has been or can be regulated by the government. Local, County, State or Fed. You become an unpaid agent for the various taxing authorities. You are bound by numerous health and safety codes. You can't discriminate against portions of the public. And on and on and on.
You can put up "No Guns" signs and enforce your will... Up until the time a law is passed that says otherwise. Conversely, you can put up "Guns Welcome" signs, up until the time your government says guns aren't permitted in your establishment.
Such regulation (for or against) are always attached to the Health and Safety of the general public. That same public you are in business with.
Private control of private property is one thing, but once you open your property to the general public, you lose much, if not most, of your control.
That being said, in areas that are not (currently) regulated, the property owner, or his agent, has the right to set the conditions of gun carry within the boundaries of the business property.
Don't like it? Let the specific company know why you are taking your business elsewhere. No reason to get into a tizzy about this. If enough people complain about the policy and it appears it may affect their profit margins, they will rethink their policies. If not, no big loss.
There are simply too many other businesses that don't care, one way or another, and will welcome you and your guns... And your money.