[gcau]

If you're just eating a burger, you're not personally slaughtering the cow. Secondly, the relationship of humans and dogs is far different than humans and cows, dogs have evolved alongside us as companions, and cows are food.

If you had to choose between a family member dying or a totally random person dying, even though objectively they're both just humans, you're going to kill the random person, because you have feelings and emotions, and they are part of the equation. For the same reason you'd kill the random person, people would kill the cow, and want to save the dog.