In the spirit of your challenge I suggest you put a sign on your place of business/property line that says "No Blacks, No Irish, and No Muslims allowed" and see what happens.
Similarly, a business owner/property owner can not deny you the right to carry a firearm. They can deny permission to persons carrying firearms onto their property and into their business, whether that person is a guest, customer or employee.
"In the spirit of your challenge I suggest you put a sign on your place of business/property line that says "No Blacks, No Irish, and No Muslims allowed" and see what happens."
I would argue that laws precluding such signs are also un-Constitutional. Yes, I recognize that such discrimination has been recognized and barred by law, but I also consider those laws onerous intrusions on the rights of the property owner. Having said that, the law still merely states that a property owner (of a public venue) can not bar a person from their property for certain, specified reasons, it does not prevent them from barring persons for reasons outside those specifically outlined in law. We've already established that a property owner can bar people from exercising Constitutionally protected activities on their private property (you kicked the satan worshipping Obama campaigners off your lawn).