It is hard to ourselves and to others and injust to oppress animals by our choices. If we want to be free, we can't cause other to lives in slavery. If we want to find our purpose, we can't steal animals purpose. If we want a peaceful life, we can't cause animals distress.
Animal products steal the lives of animals. They steal the purpose of animals. They destroy families.
Surely we want to extend our love and empathy to the most vulnerable member of our society - the non-human animals. We can create world peace between humans and humans and between humans and non-humans. It is possible if we act on our empathy, stop consuming and using animal products, and go vegan.
Wonderful lecture by Will Tuttle: http://www.youtube.com/watch?v=oLgGnP0pWzM