I stance on the question was in my post.
"My presence on their property is both optional and voluntary- as in I don't have to be there but choose to. When I choose to be on their property, I have an obligation to abide by their wishes. If I have chosen not to do so, then I don't need to be there."
When you go onto their property, it's their house and their rules. If you don't want to follow their rules, simply don't go there.
They aren't saying that you can't own a gun. They aren't saying that you can't carry a gun. They ARE, however, saying that they prefer that you don't carry a gun on their property. Bizactly. It's a preference.
Look at it this way.
If you don't want folks smoking in your living room, then I shouldn't fire up a cigar while sitting on your couch.
Why shouldn't I?
That's the same principle. I am over the legal age to buy tobacco products and can do so if I wish.
What gives you, in the example above, the right to say that I can't smoke if I want to?
(Insert your answer here.)
THAT'S what gives them the right to say they don't want you carrying a gun at their place of business.