Pits in general are great dogs. Many are some of the sweetest, best, most loyal dogs you'll ever come across.
The problem is piss poor breeding and encouraging bad behavior. When jackass hood rats and meth head rednecks breed dogs with bad traits and encourage/train bad behavior because they want a badass dog of course the damned thing is going to be aggressive and out of line with the breed standard. But with pits, properly bred and trained, it's a rarity.
Little dogs with a strong prey instinct are the ones more likely to naturally be little shits IMO.
First of all, Pit Bulls don't have a real breed standard. They are not recongnized by the AKC (and CKC is a joke registry, don't get me started)
The AKC reconginises the American Staffidshire Terrior. A good Am. Staff is basically a Pit Bull with a "good head", square, broad, with a boxy muzzle, they also tend to be a bit more blocky and broad all over.
They have the same instints as those little terriors, but are often still being bred to purpose, and it's not a nice one.
Pit bulls are the breeding dregs. Your average pit is not more then a couple generations off a fighting line. Dog fighting may be illegal, but it's still out there and more commen then you think.
That temperment breeds true. These dogs are survivalist, surviving conditions that would make anyone nuts. Sensitive to surrondings, and responding to perseved threats with aggression and dominace.
You have two types of bad owners when it comes to mastif types, bullys, and pit dogs. You have the aholes who want to "make 'em mean" and the idiots who think it's just like the Labs and Retreviers, just with bad reputations because of what they look like.
It's not just looks. I'm always wary when we have a new pit come in to board. Especially, intact males. These breeds are dominate. They can and will try to dominate anyone that comes around them.
Plus, they are built to kill. Those jaws are basically terriors on steriods. Big and well muscled.
They also generally react to fear with aggression. They very much have the mindset of "a good defence is a strong offence"
They can be great pets. Loyality and strong bonds with their people are commen. A good pit or Staff only dangorous traits should be a wicked tail wag and the ability to smother the unsuspecting with kisses.
However, it's not a breed for someone who doesn't understand what they are capable of and how their minds work. Issues with dog agression are commen. Think a Jack Russel after a rat and then understand that pit types are breed to think of other dogs as the rat. Any history with abuse or bad training can compounds these aggression and dominace traits tenfold. Every so often, you'll find one in a shelter who jumps at it's own shadow and has no cofindance, but that is not a typical example.
I dislike the misleading nature of the mentality that "Pits are PERFECT, just misunderstood!" because, while they are misunderstood, they are no more "perfect" then any other breed, and unlike some breeds, REQUIRE the work, effort and control to raise them as the great pets they can be.
I absolutly loath people that "make 'em mean." But in a way, I hate the idiots more. The ones that make 'em mean generally know better them to take them to the dog park or leave them alone with children. The idiots, on the other hand, do. And it's a terrible accident waiting to happen, and the real victim is the dog and the breed.