Sorry, Joe - ribit is neither lying nor making stuff up.
In those 33 states you mention, there ARE background checks on ALL firearm purchases from dealers, which is the vast majority of the transactions. Yes, in some states private sales are legal, and yes, some of those transactions do occur at gun shows. They also occur in parking lots, living rooms, and flea markets. Close the living room loophole!
Your claim that there are no background checks at gun shows in thirty three states is wrong.