Very well put. When I've had to kill them its because they were roos that I had no room for and could not be rehomed. I have yet to do so specifically for food but it is in the 5 year plan. When that happens though I will love my egg layers and distance myself from my food. We plan to have 2 coops just for that purpose. Right now its just the one. We've only had to put down one egglayer because she was slowly dying and suffering"Can I do this correctly? What if I mess up and cause the bird to suffer?"
Getting better at it can make that particular emotion go away--at some point you do trust that you can do it right. But I think you're right that other emotions about chicken killing don't go away over time.