Lots of people argue that rearing is all of a dogs behavior, while others argue that it's all genetics. In reality, both are true. Aggression is not defined as a temperament, or a state of being, is it a behavior. Acts such as herding, tracking, retrieving, hunting, and baiting are all to some extent aggressive behavior. Aggression does not mean that it will be harmful, as herding instincts show us. We bred dogs from wolves to take advantage of these traits because they aid us, therefore, to an extent all dogs bred for a any purpose other than being a companion, are bred to be aggressive. However, Chihuahuas and Maltese are often shown to exhibit aggressive behaviors because they are dogs and to dogs aggression is a form of communication. So, in essence, one can easily say that ALL dogs are potentially dangerous.
As far as "Pit Bulls" go, well. "Pit Bull" isn't a breed of a dog. It's a blanket term used to describe several breeds of dogs. Am Staffs, APBTs, Bull Terriers and any dog that exhibits the psychical characteristics of the above breeds. Because at least 25 breeds display these characteristics, the potential for incorrect breed identification is enormous. As a matter of fact, Golden Retrievers and Labradors have been euthanized for being "Pit Bulls" in areas where they are breed bans exist. In the opinions of many animal control enforcement agencies whether your dog is a "pit bull" or not is solely determined by the individual Animal Control Officer, who has no formal training in identifying breeds. When it comes to dog attacks, the breed is identified by the Animal Control, a vet, or the victim. Vets receive no training of breed IDing because they do not need it for their jobs. Victims are hardly a reliable source either. Because of this, is is also pretty easy to see the potential for "Pit Bull Maulings" in the news when in fact, the dog that attacked the person was of unknown origins.
In addition to this, mix breed dogs are at high risk for being called "Pit Bulls". Why? Well first most people have a misconception about what it means to be a mix breed dog. Mix breed means that over many generations many dogs of many different backgrounds have reproduced to create an animal who has an ancestry so well meshed that only DNA testing can shed any real light. For example:
http://stopbsl.com/bsloverview/impossibleid/
This link details what exactly defines a "Pit Bull" according to breed based laws. It also shows the owners dog, a mix breed commonly mistaken for a "Pit Bull". The dog gets two DNA tests. The problem with DNA testing is that there are between 400-800 breeds of dog. We have only found genetic tracers for around 100 breeds of dog. So, yes, even DNA only goes so far in this argument.
When I was little we had a Rottweiler. He was a sweet, gentle being. People say Rotties are born mean. Well it certainly is too bad that they can't see a difference between mean and protective. You see, one day my little brother Thomas wanted to go out and play(he was only three at the time). Our Rottweiler stood in front of the door and continually knocked Thomas over with his nose whenever he tried to leave. Thomas' father got upset and yanked the dog away to discover several rattlesnakes curled up right where Thomas would have stepped. A Rottweiler saved his life.
Those who say things like "When it comes to Pit Bull bans, if one jar of peanut butter had salmonella I ask for all the peanut butter to be recalled!" do not understand what responsible ownership is. Stony, our Rottie, was a great example of a well bred, well trained, well loved dog. For me to even imagine the police taking Stony away on the grounds that "all Rotties are mean" is horrifying. Are we as a society so far gone that we actually hold dogs liable for dog attacks? No... Behind every dog attack is a certain "breed" of owner. The kind that does no research on where to buy the pups, how to raise them, and what they need. Perhaps it's because he/she doesn't really care. Well I care. If it wasn't for a "vicious breed" my brother would be DEAD. That means something to me. It means something because the actions of bad owners makes all of us responsible owners look bad. That's a shame.