The way I usually explain it is that there is no actual loop hole. It’s a bait and switch term.
If the law requires you to do a background check prior to selling a firearm, you still have to do it if selling at a gun show. (This mostly applies to licensed dealers.)
If the law does not require you to do a background prior to selling a firearm, then the fact that you are selling at a gun show does not change the requirement, and you still do not have to perform a background check to sell the firearm. (This mostly applies to private citizens.)
A gun show is simply a Constitutionally protected natural right to assemble. The place where a transaction is made doesn’t change the law.
Considering that private citizens are not allowed access to the NICS checks, “closing the gun show loophole” is code for banning private sales at gun shows (or perhaps banning private gun sales all together).
Thank you. I will keep that in mind for future arguments.