Actually, it is prohibited for a dealer to show a handgun to an underage person. The common practice is to for the dealer to show the gun to the parent and then the parent can show it to the juvenile but that is not legal per ATF as the juvenile is still in possession of a handgun. Here is the actual wording from ATF:
Juvenile possession of a handgun on the business premises of a licensee for examination or viewing purposes is prohibited pursuant to 18 U.S.C. 922(x). Under 18 U.S.C. 922(b)(1), it is unlawful for a Federal firearms licensee to sell or deliver “any firearm or ammunition to any individual who the licensee knows or has reasonable cause to believe is less than eighteen years of age, and, if the firearm or ammunition is other than a shotgun or rifle, or ammunition for a shotgun or rifle, to any individual who the licensee knows or has reasonable cause to believe is less than twenty-one years of age.”
Further, 18 U.S.C. 922(x) provides that it shall be unlawful for a person to sell, deliver, or otherwise transfer to a person who the transferor knows or has reasonable cause to believe is a juvenile - (a) a handgun; or (b) ammunition that is suitable for use only in a handgun. And, it shall be unlawful for any person who is a juvenile to knowingly possess the same. This subsection does not apply to--
A. a temporary transfer of a handgun or ammunition to a juvenile or to the possession or use of a handgun or ammunition by a juvenile if the handgun and ammunition are possessed and used by the juvenile--
i. in the course of employment, in the course of ranching or farming related to activities at the residence of the juvenile (or on property used for ranching or farming at which the juvenile, with the permission of the property owner or lessee, is performing activities related to the operation of the farm or ranch), target practice, hunting, or a course of instruction in the safe and lawful use of a handgun;
ii. with the prior written consent of the juvenile's parent or guardian who is not prohibited by Federal, State, or local law from possessing a firearm, except--
I. during transportation by the juvenile of an unloaded handgun in a locked container directly from the place of transfer to a place at which an activity described in clause (i) is to take place and transportation by the juvenile of that handgun, unloaded and in a locked container, directly from the place at which such an activity took place to the transferor; or
II. with respect to ranching or farming activities as described in clause (i), a juvenile may possess and use a handgun or ammunition with the prior written approval of the juvenile's parent or legal guardian and at the direction of an adult who is not prohibited by Federal, State or local law from possessing a firearm;
iii. the juvenile has the prior written consent in the juvenile's possession at all times when a handgun is in the possession of the juvenile;
iv. and in accordance with State and local law;
B. a juvenile who is a member of the Armed Forces of the United States or the National Guard who possesses or is armed with a handgun in the line of duty;
C. a transfer by inheritance of title (but not possession) of a handgun or ammunition to a juvenile; or
D. the possession of a handgun or ammunition by a juvenile taken in defense of the juvenile or other persons against an intruder into the residence of the juvenile or a residence in which the juvenile is an invited guest.
Therefore, juvenile possession of a handgun on the business premises of a licensee for examination or viewing purposes is prohibited pursuant to 18 U.S.C. 922(x) as it does not fall within one of the enumerated exceptions.
That said, the salesman was still a jerk.
