First post and you are bullying folks.
I'm not sure I ought to say "Welcome to OCDO".
There are ways to tell folks off, and there are ways to tell folks off without making them hate not only you but everybody else like you. Starting off a conversation with "See this gun on my hip" may not go much further as the person you say that to may suddenly be busy dialing 9-1-1.
Presuming OC is legal where you live and do your shopping, it might be more advantageous to ask the shopkeeper what motivated them to post against carry and see if they are willing to discuss the issue. If not, then get the word out that they are not OC-friendly or even not RKBA-friendly - if that is the case - but do not keep going to them and getting up in their face about the whole thing. It does not help your situation and it certainly does not help the cause. See, they sit around at lunch and after work with folks they know, who are probably other business owners, and talk about the customers they deal with. They also do that at the Retail Merchants' Association (or whatever else they have) meetings. If you wanted to make sure every merchant in town got the word that gun owners were in the top half of the top ten worst folks to have to deal with you could not pick a better way to accomplish that.