This term appears to have taken root in the early 1990’s, just after pit bulls spent the 1980’s on a killing spree, (which has only increased since). During the 1980’s, the pit bull breed amassed 45 deaths versus the next top killing breed, the German Shepherd, which amassed 13 in the same period. The Rottweiler community adopted the same verbiage in 1996, just after the breed catapulted to the top killer from 1993 to 1996. “The most ‘maligned’ breed” terminology, however, is primarily used by pit bull advocates in an effort to gain sympathy for the dog.

The stranger may see only a “pit bull” on a leash held by an obvious fool. Your behavior and the behavior of your dog may be the only opportunity this stranger will ever have to see the positive side of what has become the most maligned breed in the history of dogdom. – American Pit Bull Terrier Handbook