Unless you have a concealed carry permit, you are only legally allowed to carry in full view. If they have a normal carry permit, it does not allow them to conceal it.
If they keep it in the holster, there should be no issue.
If they are waving it around, then you should call the police over there, and let them handle it.
If you are carrying and do not have a concealed carry permit, it is you that is breaking the law and giving the ones that openly carry a bad name. Of course, if you have a concealed carry permit, then you probably wouldn't have made your earlier post.