I've actually done this more than once.
Couple months ago, to manager at formerly-favorite restaurant with new idiot signs:
"Hi. I've been coming in here for many years. Now I see your sign, that you don't allow guns. Is this a corporate decision or just your store?"
"It's corporate"
"OK, well, I just want to verify that you don't want my business - is that correct? I carry a concealed gun, so therefore I'm not allowed - is it true that you don't want my business any more, even though I've been coming in here for years?"
"Yes, that's correct. But, if it's concealed, who's gonna know?"
Me: "Huh? Say what? It's YOUR sign, that says 'no guns'. It doesn't say 'no OPEN guns; concealed ok' - I'm trying to obey YOUR rules, and verifying what they are. Are you telling me to ignore your rules?"
"Well, no I guess not. But people carrying open scares the customers."
"Well, I'd like for the sign to be taken down."
"Well it's not gonna come down."
"Well, in my opinion and belief, it will either come down or you'll go out of business in this very pro-gun state. It already looks much slower in here than it used to."
"Yeah, well you may be right, down here in this state." (I sort of inferred that he was from elsewhere, of a more northerly latitude).
"Ok, I'll check back every few months to see if the sign is down. "
"OK"
There is NO WAY I'm giving one dime of my money to a business with a stupid sign, even if the mgt tells me with a wink and a nod that they don't REALLY mean it, for a 'good' customer like me carrying concealed. Screw them.
Having said that, and maybe this is a cave of principle (not sure), but there ARE some places here now that open carry is legal, which used to have no signs, but recently put up signs that say "Concealed only" with a picture of a handgun. I'm ok with these, and still give these places my business.