No Guns or Property Rights Allowed

So I was working off site today, at a plant owned and operated by my company but located on another company's property.  The sign on the way in says...

NO GUNS ALLOWED

PERSONNEL AND VEHICLES MAY BE SEARCHED

Now I knew going in that the company I was visiting had a pretty strict anti-gun policy, but apparently since their headquarters has moved to Chicago, it has gotten even worse.  I have a license and typically carry every day, but today was a definite no go.  I felt completely naked and a little ticked off.  I really dislike when property rights and self defense rights cross paths and purposes.

EDIT:  The company states on its website that they are a long-time supporter of the NRA...hmmm