Irresponsible people lead to different breeds being branded as "bad." At one point Dobermans had a bad rep. Then Rottweilers. Now it's pit bulls. Part of it is indiscriminate breeding of the dogs. Part of it is people who mistreat the animals to make them big and bad.
The breed was created for "bull baiting" in Britain. The dogs were put in a ring (pit) with a bull to harass it for hours on end. Pits are a terrier breed. Terriers by their nature are tenacious. Today there are dogs labeled as pit bulls, when in reality they are a mishmash of all sorts of breeds.
My BG (Big Goof) was labeled a pit bull by animal control when I adopted him. My vet and I think he is part pit, part bull dog, part boxer, part Dalmatian and part some kind of hound. He is a big old goof with people. He is afraid of my cats after Mikey (cat) smacked him in the face. On the flip side, he loves to chase lizards and snakes. He's killed several snakes. Killed a skunk. Kills rats in the barn. He is obsessed with the gopher tortoises on the property. I trust him with people, but not other animals because of this.
My answer to your question about whether it's media hype or actual bad behavior by some of the dogs is that I believe it is some of both. I know some absolutely sweet, loving and lovable pits. And stories about dogs killing people sells newspapers.
For another interested in the truth about the breed, I recommend the book "Lost Dogs." It's the story of the dogs Michael Vick had on his property. Of the 52 dogs rescued only two had to be destroyed. One was a female who was bred so many times her health was so badly damaged the kind thing was to put her down. The other was a male who fought so many times he'd been made vicious. The others went on to be pets, therapy dogs, or live out their lives at Best Friends rescue.