Something just seems wrong about a gun show, of all places, not allowing those with a license to exercise our Constitutional right to bear arms to exercise that right. It's like a seminar on free speech where there are strict codes against saying anything critical of government, or a seminar celebrating the 4th Amendment where the attendees are protected by random searches of those who enter.
It seems to me that a no guns sign at a gun show would increase the chance of cars being broke into, since it would be obvious to criminal types that a relatively high proportion of cars parked there would have a gun in them.