I own a few chickens for the sake of eggs, named them as well, and while I'd happily eat chicken and rice or any other derivative of eating chicken I wouldn't just go out back and carve up one of our hens. I definitely think it's because of the ascribed personality to the animal/creature. Pokemon are well established to be able to think independently, have their own personalities, and many are quite weak in the wild to the point of having near useless attacks. Introducing the ability to have those creatures die isn't bad on its own, there can be gameplay merit to that, but the line for me is when you make a visualization of it. When you take that feature and expand on it and advertise with it.

Sure, your pet will die someday, probably peacefully in its sleep but something like Palword says "What is we make it violent?" It's as visceral to me as someone saying to you that your pet chicken would make some really good nuggets and proceeding to butcher them in front of you, acting disconnected afterwords and saying something to the effect of "What? It's just a chicken."