Oh I don't know, trespassing with a firearm is a serious crime in most states.
Ignoring the lawful wishes, and rights, of a *private property* owner to decide who and how someone enters their *private property* is probably not the best way to extend good will. It certainly puts responsible gun owners in a bad light.
Check your local laws, but this is something most people don't understand. If it's posted "no guns" or you are otherwise aware that you are not allowed to carry a firearm on the premises then you are committing a crime (trespassing) when you enter anyway. A lot of people seem to think that you have to be asked (or told) to leave before you are trespassing; not so. If there are rules to entry you must follow those rules, or by default you are trespassing.
I'm not saying that it does not suck to be kept from entering an establishment while carrying. It does. But at the end of the day if it's private property then you really don't have a choice. Your rights, First Amendment, Second Amendment, or otherwise do not necessarily extend, or apply on private property. In may cases the rights of the private property owner outweigh your individual rights.
It certainly does not help anything if your going out of the gate with an attitude that you don't care about other peoples rights.
I would maybe ask the management to post the sign of "No Guns" but as that they amend it to allow concealed carry license holders: "No Guns, unless licensed under ORS 166.291 and 166.292" ORS = Oregon Revised Statues and the ones listed are the concealed carry license provisions, substitute with your own states obviously. Extol the virtues of concealed carry licensees - background checks, law abiding, etc.
Also, keep in mind that may places put these signs up to reduce liability. If you talk to the owner, or manager, you may be able to get permission (I'd get it in writing or record the phone call) to continue to carry despite the posting.
Always, respect the right of the private property owner though, not doing so puts responsible guns owners and concealed carry licensees in a bad light. Always keep in mind (and remind the owner/manager) that you do not have to enter/patronize their property/establishment. Business worships one god - the dollar, keeping people away is typically not in their best interest.