Comment by slothtrop
Morality is arrived at through value judgement. We have a social contract with each other, not animals.
People generally dislike gratuitous pain and cruelty, hence we're seeing a push for cage-free hens and the like. They don't oppose slaughter in and of itself.
What people generally oppose today is a function of their consciousness and ability to access alternatives. They don’t oppose slaughter because they don’t think there’s an alternative, the same way that a person who is on the verge of starvation will steal food. They also don’t oppose slaughter because it’s hidden away from them, and done by others.
Slavery is an excellent cognate to this.
It’s a slippery slope, isn’t it? If you’re not careful with your compassion, you’ll end up having it for all sorts of beings you’ve come to see as like yourself.