what's the right job for a tool whose only use is to kill or severely injure living things?
Firearms are used for any number of target shooting type competitions, from young people shooting in Appleseed competitions, to the ultra long range competitions like the Camp Perry type stuff.
There are re-enactment type of events, such as cowboy action shooting...
While firearms are excellent tools for defensive, or offensive "killing or injuring", it most certainly is not their only purpose.
Thomas Jefferson thought so, as well....
In 1785 Thomas Jefferson wrote to his fifteen-year-old nephew, Peter Carr, regarding what he considered the best form of exercise: "...I advise the gun. While this gives a moderate exercise to the body, it gives boldness, enterprize, and independance to the mind. Games played with the ball and others of that nature, are too violent for the body and stamp no character on the mind. Let your gun therefore be the constant companion of your walks."1