It is less personal if you're processing a number of birds at the same time and not just one.
I name my birds things like Dumpling, Noodle, Stew, etc. as a reminder that they are livestock, not pets.
Do you know which aspect of the job bothers him the most?
What bothered me most during the process was the flapping -- I was using the broomstick method so holding a frantically-flapping bird by the ankles was a bit disturbing until I understood that the really STRONG flapping indicated the swiftest, most effective, most merciful killing. We're considering trying killing cones to see if it's more efficient, especially because the arthritis in my wrists is worse now.
You might consider the different methods to see which is the least upsetting.
My husband doesn't want to do the killing himself, but thinks he could handle the other parts.