Religions are often a bundled group of morals and values. Some people may choose not to adhere to or follow the principles of the religion they choose, but itself would show a lack of conviction for thier beliefs.
Someone specificly choosing to wear a symbol that states such beliefs, and then not adhering to the beliefs they choose to adamantly state to others would clearly be a hypocrite.
If someone chooses to be a part of a group that espouses certain values that will impact decisions they make in thier life, and then chooses to advertise to other people they have those values with symbols, it becomes a very legitimate basis for some discretionary judgement.
If I was to put on clothing or a tattoo that said I was a member of a certain gang or organization with certain views, that would be a legitimate thing to judge me on that I choose to inform you of.
If I choose to wear a piece of clothing or jewelry that states I am from a group with certian beliefs, then you can judge me on it.
If someone made a religion that espoused beliefs that it was okay to steal because everything is of the earth, and the earth belongs to no individual, but to everyone...and someone wore a symbol stating that was a religion they were a part of, would you want them in your store?
It would be your right to ask the very likely thief to leave.
You would be basing your decision on core beliefs they chose to make you aware of through the advertising of thier religion to you.
Religions are often core values people base many decisions on. If you cannot judge a person based on thier core values, values they choose to make known to you by clearly stating it with clothing, jewelry, customs etc then people really have no freedom.
The government is forbidden from discriminating based on such things, private parties are not supposed to be. The government is forbidden from passing laws that restrict or infringe on the right to keep and bear arms. Private businesses and homes still have the right to discriminate.
To me that means no law should exist that create legal punishment for someone carrying concealed against the wishes of a private party, as that would be the government taking an active role in infringement on the behalf of the private party.
At the same time that private party can ask them to leave for any reason at any time. Refusal to leave is tresspassing. Whether it is because they don't like thier breathe, thier religion, thier carrying of a gun, thier clothing etc
So 'no gun' signs should always be unenforceable legaly, but the business can and should be able to bar anyone entrance or have anyone leave if they become aware of a customer doing something they do not want done. Whether that is wearing the wrong color, thier possession of a firearm becomes known, or they have a symbol that states certain beliefs on them.
This may of course become a serious issue when most businesses in the future have cameras that can detect concealed weapons. Such cameras already exist and are being used in some nations. They will become cheaper every year.
http://www.cnn.com/2008/WORLD/europe/04/16/camera.england/index.html