A 2013 study conducted by Erin E. Buckels et al had some interesting things to say about sadism.
Sadism is not just associated with a fetish. It is also a rare, but existing behavior trait that has some people take pleasure from hurting others. This is not necessarily psychopathic behavior. Rather it distinguishes itself because people seek out the opportunity to hurt others.
The study revealed that given the opportunity to engage in aggression facets of Dark Triad personalities came to the fore. However, it was only sadists who were willing to work for the opportunity to harm an innocent victim.
Sadists independently predicted behavior reflecting ‘an appetite for cruelty.’
The study concluded that although sadism is rare, it is more common than we think. Equally, good manners and the way an individual treats you at the social level might give you an indicator as to whether you are dealing with a Sadist or not.