Think about it this way. There are those who are saying that they support the idea of a business being able to control whether or not guns are allowed there.
I have the perspective of living in a state which has a different law. The state, and ONLY the state decides where you can and cannot carry. A business can post a 'no-guns' sign, but it holds no force of law. A business owner may refuse service to anyone for pretty much any reason. If you come in with a gun in plain view, they may ask you to leave, just as they may ask ANYONE to leave. If you REFUSE to leave, you are committing trespassing, not a gun crime. They have no police powers to search you, and if you conceal correctly, they will never know. This is really win-win. The business owners don't have to worry about the horses getting spooked, and the law-abiding gun carriers don't have to make a crap-list of all the businesses they don't support.
There is a in-mall theater here with a 'no-guns' sign. I have ignored it and carried there frequently, because it happens to be the closest theater to my house. Then my conscience got the better of me, and I decided that I shouldn't support anti-gun businesses. THEN, I happened to meet an employee of the theater. He said that not only do the local management not care if you are carrying, a couple of members of the management have their permits and carry there frequently, since there is not a corporate policy forbidding employees from being armed on the premises. Corporate says to show the sign, and they do, but they have never turned someone away because they thought they were carrying.