I don't think it's so much that you're numb to it - you just don't see it as something to fret over.

I grew up around livestock and quail hunting while we didn't butcher anything with hooves ourselves, I saw my fair share of animal husbandry work and quail cleaning (and fish cleaning) and it just doesn't phase me. I never had to steel myself against the 'horrors' of it - it just was what it was.

I'm pretty sure that's right where Palin is. For her, there's nothing more to flinch at than if she was in front of an automaker tightening a bolt. It's part of their work, something they do every day, part of the process of how we get our food. Kinda like a Dr. wouldn't think twice about standing in front of an operating table with some guy's knee being repaired during an interview (other than his/her worrying that the germ-free environment might be compromised by a cameraman). It's just part of life.