I raise English Mastiffs and french bulldogs and have for over ten years now. Some breeds are more aggressive than others due to breeding. Anecdotally , based on people i have known and what they have experienced, bull mastiffs have been responsible for more attacks than any other breed. This includes attacks against more than one family member in a home in which the dogs they have were well treated. There has been no problems with the other breed dogs that they have. In another case, a person who shows dogs in the ring professionally , had the bullmastiff for the day, fed the dog, showed the dog, and put the dog in the car. She forgot something in the car and when she bent in to get it the dog repeatedly bit her in the face. Another aggressive breed is the american bulldog. Some breeds make good family pets and some do not. That is not what they were bred for. Male dalmations and young children are not a good mix. There are exceptions ,but it is much wiser for the family and better for the dog involved if dogs are matched up to the what they have been bred for. Some dogs are fine with people but not good around other dogs. Female bulldogs and french bulldogs, are very territorial and try to dominate other female dogs. I agree that many dogs who attack people or other animals have been "trained" to do that or have been abused. There are breeds though that are just more aggressive.