In to kill a mockingbird why doesn't atticus like to shoot guns

When he gave us our air-rifles Atticuswouldn't teach us to shoot ... Atticussaid to Jem one day, "I'd rather you shot at tin cans in the back yard, but I know you'll go after birds. Shoot all the bluejays you want, if you can hit 'em, but remember it's a sin to kill a mockingbird

Atticus doesn't like shooting guns because he thinks that his good shooting skills God has given him is an unfair advantage over living things. The answer is that he believes a real gentleman never takes advantage over any living thing.