I think nothing of folks calling firearms the following...
guns
rifle
pistol
pistol-ee
hog-leg
pop-gun
weapons
firearms
tools
buddies
arms
boom-stick
hand-cannon
My life-long freinds use these and others and it means nothing to me b/c I understand the context in which they use them. Usually ... 90% of the time we just use the word "gun"

It is way more important to know the person and the intent of use. If you have a concern about this I'd ask the guy straight up. What's wrong with a simple honest expression of your reation to his use of the word. Let him explain himself....You don't have to sell it to him, it's not a rental ... you can sell it to whomever you like.
Having respect for firearms and the sanctity of the life of game doesn't mean you must always use a certain lexicon else you are a boor......