There is a difference between humans, and other animals. Yes, humans are animals, but there is a very large distinction between the two. Which is why we are not classified as just animals, but the classification system goes much further.
Yes, there are some sick treatment of animals out there. However, a lot of it is also over exaggerated. I've worked on various farms, and the animals, for the most part, are treated very humanely. And the thing is, people raise those animals for nothing more than to be food. Abusing the animals produces a lesser quality product, which fetches less money, and thus is a loss for the business.
Again, yes, some of the treatment, in some facilities, are not always the best. But that is a minority, and is greatly blown out of proportion. And yes, there is a difference between humans and animals. Killing chickens is not like exterminating Jews during the Holocaust. That is simply insulting, and devalues human life, which is why the whole thing even happened.