Humans Sacred?

I was going to comment on Bretsky's post about holding humans as sacred and it became a whole post in itself as I thought about it. If I don't see all beings as sacred, if I am not as willing to die for a tree or for an animal as I am for a human, then do I really hold anything as sacred.

I once participated in a program with Barbara Marx Hubbard. She holds the position that we are all cells in a larger body, the universe. So we are part of a sacred collective. It seems to me at times that human beings act more like cancer cells in this body than benign cells. Like cancer cells, it seems as if we don't care if we kill our host in the process of getting more of what we want or having things our own way. It seems that our collective and individual contempt for other beings is what allows some humans to destroy rainforests and kill animals for their fur or tusks. We are certainly on the path to destroying perhaps a whole planet and the life forms that inhabit it.