I guess you can agree with him that that is not hunting, nor is it meant to be. If he had a barn full of rats, would he insist on killing them one at a time? Hogs are not protected because they are considered a dangerous, invasive pest, harmful to the native environment and native species, and as such are not afforded a hunting season.
I saw a documentary on the problem of raccoons in Japan. Apparently in the sixties there was an introduction of raccoons as pets because of, I think, a cartoon. When they realized that raccoons do not make good pets their owners just released them. Four decades later the raccoon population exploded, and the raccoons are destroying the wooden houses and shrines in this area of Japan. Now all raccoons are killed on sight. It is heartbreaking, because it was the ignorance of people that caused the problem; it wasn't the raccoons' fault, but they pay the price. Starlings and English Sparrows were introduced into Central Park (to honor Shakespeare), and now they are successful competitors of native birds like Purple Martins and Bluebirds, and they are also not protected (and again, it's not their fault). We've got to stop being so short-sighted.
By the way, was the trapper able to donate the meat? There are lots of people here who would be very grateful to be able to fire up the grill and feed them to their families.