i think most people place a higher value on human life then animal life (it's lead to some very interesting debates on this site including the treatment of our own fish). therefor, it's a HUUUGE step for most of the population to go from mistreating an animal to mistreating another human. it's amusing to me to see that people are equating this with psychopaths and future mistreatment of another human.
i bet there's more people who have done stupid things in their developmental stage involving any form of animal life and lived a normal productive adult then there are that ended up true psychopaths.