Calling a gun show a "gun free zone" is obviously not accurate.
There are guns on display by dealers that are not zip tied. I don't know why they get away with it but they do. It's mostly long guns where I see that so that might have something to do with it. I've operated the action on many used guns at gun shows before. Those same dealers usually have ammunition within arms reach of their guns. They could easily respond to a threat.
I have taken handguns to have them appraised. They always get zip tied at the door. I may or may not have a loaded magazine or speed loader in my pocket. I've never been asked if I have ammunition on me. It would take me about 10 seconds to open my knife cut the zip tie and load my weapon if something went down.
Up until yesterday Speedracer didn't know that guns must be zip tied. How many other people that don't attend gun shows don't know that? Anyone that attends shows regularly knows that it would be stupid to try something there.
If I was intent on killing as many people as I could I would just as soon walk in to the Harris County Greenspoint substation as I would walk into the Pasadena Convention Center during a gun show.