I agree it is not the breed as the whole. It is individual dogs that were bred knowing little about their genetically controlled reaction to stimuli or bred for the wrong reactions to stimuli.
The "jerkoffs" are likely breeding temperamentally unstable dogs. Pet breeders who never test the adults for their genetically controlled reactions to stimuli could also be producing unstable pups. When loving pets (never exposed to stimuli that would elicit the genetically controlled reactions) are bred, there is no way of knowing what genetically controlled reactions (or how intense) the pups may have. For example, if you bred two pet Border Collies (having never worked them on livestock) you will have no idea how the pups might respond to livestock. If you breed two pet pit bulls (never putting them in stressful situtions that might elitic animal agression or human agression) you will have no idea how the pups might respond to these same stimuli. Think of it like breeding without testing for "carriers" of a gene; if you don't test for the gene you have no idea if you could be passing that gene on.
Both types of breeders are likley contributing to the number of unstable individual dogs within the gene pool. As the numbers of these dogs in the gene pool increase the genetics of the breed as a whole will drift away from what it has been.