Come on - that's too broad a stroke. There is the concept of differential risk situations.
Whether that applies here is the argument. Is the show a peculiar risk, attractive nuisance, etc.?
Not saying it is and I don't like carry restrictions but overly generalized arguments don't help.
I dunno. A concealed gun at a gunshow should have no bearing on the show and no bearing on safety, but basically the signs are saying that they don't trust people with loaded guns at the gun show. Sadly, of the incidents about which I have knowledge at north Texas gun shows, all of the incidents have been by vendors, not patrons.