It is not opinion, it is the law. The State of Texas has written into the code of law that signage properly placed prohibits weapons on the premises or in the establishment where found is that sign. That is the law. If you violate the law, you will be arrested. Pretty simple concept.
Although I own a gun, have a CHL and believe I am responsible enough to carry (at least concealed) anywhere, I still must follow the law. When each individual decides to become the law, the term for that is "anarchy" and that is a very undesireable living environment.
“It is not opinion, it is the law.”
Seemed more like an opinion than the law when you wrote “You should have the right to state the rules for your own property.“
But it doesn’t really change my questions much. They’d now be: But what is the basis for that be it opinion or law? What would you say to convince someone who disagrees with you that you are correct and they are not?
And the fact that it is Texas law doesn’t mean much. Laws change. If there was a movement to change that Texas law or change the law in any other state, and those on one side took the position that “You should have the right to state the rules for your own property“, what would the answers to my questions be?