For some (such as I) animals have always been there for me when the people weren't, so I will quickly admit that it hits my 'emotion' button.
Also, I work around some of these 'people'. Some of them as young as 4 (who stabbed a puppy to death). They really, REALLY do get off on the suffering of another being, and it excalates. After being around them for a bit, I walk out grateful that I have a key and they don't.