Pit bulls are widely seen as extremely aggressive and dangerous dogs. Critics say today's pit bulls descend from the English bull-baiting dog, which was bred to fight bulls and other large animals for entertainment. Because of this, pit bulls are just naturally more dangerous in terms of their personality and physical ability to cause harm. Just like how herding dogs are more likely to herd than a poodle, it's possible that some dogs are genetically predisposed to being more aggressive.
That's not to say all pit bulls are bad. Obviously, training and environment both play a huge role in how a dog acts. Critics say pit bulls are just too high of a risk to have in society. There are no real reasons to own a pit bull beside companionship. Dr. David A. Billmire argues banning the breed would protect humans from unnecessary harm:
Based on my extensive experience, I believe that the risk posed by pit bulls is equivalent to placing a loaded gun with the safety off on the coffee table. In my opinion, these dogs should be banned. I know this is an unpopular stand in some circles, but how many mauled children do we have to see before we realize the folly of allowing these dogs to exist?
The arguments made by advocates of these dogs are the same arguments made by people who feel that assault weapons are an essential part of daily living. There are plenty of breeds available that peacefully coexist with human society. There is no need for pit bulls.
Pit bull advocates say singling out the breed does little to address the problem of dog bites and maulings. It's true that pit bulls are descended from dogs that were bred for fighting. That doesn't mean anything. Other dogs have been singled out for their reportedly dangerous characteristics over the years but none of those bans stood up to scrutiny. The call to ban pit bulls is the same:
Laws of this type can be traced back to at least the late 19th century, when fluffy white “spitz” dogs were persecuted on the mistaken belief that they were uniquely susceptible to rabies. Soon after, Massachusetts banned bloodhounds and Great Danes on account of their supposed “viciousness.” And in the 1920s, a New York magistrate urged that German shepherds be regulated because they were “bred from wolves.” Each of these outcries reflected the media-driven hysterias of the age. Today’s breed bans are no different; only the targeted dogs have changed.
Genetics can determine a lot about a dog, but it's not what ultimately determines a dog's personality. Training and the owner's demeanor matter way more than a dog's ancestry. Pit bull advocates say the stereotype of being a fighting aggressive dog has attracted bad people who want to use pit bulls for bad purposes. The problem is with people, not pit bulls:
Cynical politicians tend to frame the need for breed bans in zero-sum terms: Either you care about public safety, or you care about animal welfare. What gets lost in the divisive rhetoric is that there’s a superior alternative: Ordinances that hold every dog owner to the same high standards of civic responsibility serve both interests equally.