Your neighbor is raising chickens the way they have been raised for thousands of years on farms worldwide. Thousands of years. I understand how much horror that brings out in many people but I will point out they are not dead yet. That's almost certainly the way his father and grandfather raised them. Your neighbor may be crazy or his attitude may just be different from yours. He probably thinks you are as crazy as you think he is.
Those are his chickens. If you lock them up that could be considered theft. From your screen name you are possibly in Oklahoma. I don't know what your state laws are about that. If they are on your property you may have certain rights, but that's usually only if they are causing damage. You can chat with your local law enforcement, or probably better your local animal control, to see what they say or you can do as you will. I don't know what the consequences might be.