This seems to me to be a relatively minor annoyance though, compared to being ejected or the police called.
Also, if you OC somewhat discreetly, it is far less likely that the WalMart greeter, if any (sometimes there are none at my nearby WalMart), will even see your gun. The general idea behind open carry in public is you go about your daily business and show that this does NOT cause any problem, alarm, etc.
What is discreetly? Maybe somthing like - Dark gun on dark clothes. Small to medium size gun in holster blending with clothes. General grooming and clothing appearance that does NOT draw attention to yourself. Looking like you just came from the bush wearing hunting or para-military regalia, gun vests, etc. is not discreet.
Hint: Do try wearing Kakis, or even nice shorts, plus clean collared shirt.
Don't loiter - go in, shop, pay, leave - keep moving.
Use a holster - the sticking it in down your pants thing is for bad guys.
Be calm. I like to keep an object like a cup of coffee or keys in my carry hand - it give me somthing to do with my carry hand and assures me no store camera will ever catch me even remotely touching, or getting my hand nearmy gun for even an instant.
Smile, but don't flirt or get cute with people or preemptively engage total strangers in conversations about gun rights, politics, etc.
When possible, bring a friend or family member with you - preempts the "lone gunman" idea.
If you sit at a booth for lunch, sit gun side to wall. If at a table, sit so gun is discreetly out of view as much as possible. Never linger near or sit at a "bar" like object in a restaurant. Don't order or consume alcohol, even though it's often legal to do so.
What you want is for folks at the end of their day around the family dinner table to say something like, "Honey? I think I saw a man wearing a handgun near the mall today - he did not look like a police officer or security guard, he was just picking something up at Best Buy, etc." That gives others at the table the chance to chime in, "oh yeah, it's legal - a lot of folks are doing it now according to press reports," etc., or so some research on the topic and find out more.
I chose this thread to vent a little - John and I get emails from folks explaining that they were "hassled" for OC - but often it turns out they were unnecessarily drawing attention to themselves, like sitting "atthe bar" and their back and gun to a crowded restaurant, etc. or they were wearing shoulder holster and sweeping the public with their barrel(s).
These "hassle" incidents are failures for us - they force store management and politicians to look at restricting rights to deal with these incidents brought on unnecessarily.
I have open carried for years in many public venues in Virginia, Pennsylvania, Kentucky, Ohio, and North Carolina - including WalMarts (where one time two police officers walked right past me and I only detected ever the small "eye roll" from one officer), grocery stores, malls, etc. And except for one time being asked to leave a restaurant by a legally confused manager, I have never ever been confronted by store management or the police, or even a (visibly) angry anti.
Only once did a person choose to speak to me and object to me carrying a gun - but as I paid my bill and left I calmly did a little Columbo impersonation - "Ah, well, oh - you know, I just carry for normal self-defense, don't mean any harm." The lady then looked at me and my little daughter going about our business and her frown transitioned to one of perplexed puzzlement. I said "have a good day" and she said "You too."
Other than that, a few neutral or positive comments or questions and stares now and then, but that's about it.
Am I lucky - I doubt it. And I doubt most open carriers ever get hassled either.