Am sorry for those traumatised by the actions of aggressive dogs.
Dogs at best have the intelligence level of a 4 year old human and those that have dealt with 4 year humans know that these require a lot of "guidance".
It is the "guidance" part, that is more often than not neglected, thereby resulting in "incidents". This more so with breeds hardwired to "protect".
Having said that, I believe that dogs are a person's best friend and some of the incidents are triggered by people, example: people coming to pet dogs without the owner's permission or neglecting the owner's request to stay away.
BTW, if your dog attacks a thief in your own home, the thief can sue you for dog bites, this in the province of Ontario.
For those with dogs, check out this excellent training school:
Private or Corporate Canine Services
www.caissiecanineinstruction.ca
* an ex-owner of a (beloved) Boerboel *