The OC thing is creating an unresolved (and likely ignored) conflict.
The libertarian inside me agrees, it's the business owner's right to refuse service and his right to bar people from carrying guns into his establishment.
That same libertarian voice also says that he can do that for any and all reasons, including because the customers are gay, black or Jewish.
In reality, he dare not refuse to serve someone base on sexual orientation, race or creed. Because rights.
If he can refuse to serve or bar guns, it's not a right based on how other rights are treated in the marketplace.
You can try it at home by changing the actors and seeing if the phrase you are using changes from reasonable to unreasonable.
Such as, "How dare they go out in public as Jews?" instead of "How dare they go out in public openly carrying rifles." Is that illustrative?
With all that said...
Having the right to do something doesn't always equate to it being a good idea to do something.
It's perfectly legal for me to set up a firing range in my back yard. If I start shooting, there's going to be problems with the neighbors at a minimum and a visit from the sheriff's department in all likelihood (prolly with guns drawn).
The balancing act is rights vs manners.
The businessman probably should have a right to tell black people to shop elsewhere. It's rude and it's likely a poor business decision nowadays because he'll get backlash from people who don't care for racism.
To show that I learned what more than a couple people tried to teach me: What the OC people did was rude to their fellow customers and the business owner, by tolerating their further presence, risks a backlash from people who don't really feel comfortable around guns. We'd have to basically guarantee Chipolte Grill that we'd make up for all that lost business if they let rifle OC continue.
A problem I've mentioned before is that these large corporations are far more worried about the loss of revenue from people boycotting them over the issue than the actual danger of the presence of the guns or the discomfort of people who've already paid.
The OC people provided the excuse to do what they'd been wanting to do all along, ban guns from their stores. This excuse gives them the cover they need to avoid the backlash that an unprovoked ban would cause. Think back to how Starbucks worded their press releases before they finally had had enough of us and how we rejoiced at their being neutral.