Nope. No law saying one SHALL not open carry. There is also nothing that says one cannot be a test case for a disturbing the peace call to the police if someone puts up a fuss by seeing your openly carried weapon either.
Soooooooo, who would really put their permit on the line just to try a point?
Legal and wise are not mutually inclusive. It's also legal in MD to marry your cousin but it is not necessarily wise.....