How can people be so cruel and evil to such innocence?

I have really lost faith in the human being. I read about a guy that continued to hit his girlfriend's dog against the wall until there was blood all over the place and the dog had internal bleeding and brain trauma. He then choked the dog to its death. All because the dog pooped on the floor. I read so many of these kinds of stories that it is making me think that the human race is just no good. I find myself feeling no respect for the human race at all. I can't even fathom this kind of behavior as even the thought of it sickens me. Our pets are so innocent, totally dependant and totally devoted to us. Our dogs especially. How could anyone do this kind of thing? It goes beyond my comprehension!