Just because they are worth less than a human doesn't mean you are free to inflict pain and suffering upon them. I'm vegan and i see animals as below me, i'd kill an animal if it means saving a human life. However that alone doesn't justify paying for them to be abused, raped, and have their throats slit for 15 minutes of taste pleasure when i can just eat something else instead.

The line is to not hurt animals unless you have a reason to.