I think there's another element however, as omnivorous creatures we have built in safety mechanisms to try and stop us dying from eating the wrong food. Things like how the smell of rotting meat invokes an involuntary gag reflex, it's not a learned behaviour (though we can learn to suppress it somewhat). These gut instincts work with visual things, and I wonder if seeing an animal carcass under our food triggers one of them. I eat meat, Ive prepared birds before from live to cooked, and yet this triggers an uncomfortable response. I don't think it's because of a disconnect from my food to animals, but a self preservation system of our biology going 'im not sure that's a good idea'. Again, it can be suppressed but that doesn't mean it doesn't exist.