Animals are unpredictable and can snap at moments notice. When that happens with most dogs it doesn't usually end up deadly but pitbulls are just so much more powerful they tend to kill more often.
what is depressing is how people speak in generalities and not facts, doing more harm than good to the breed.
http://www.aspca.org/pet-care/virtual-pet-behaviorist/dog-behavior/truth-about-pit-bulls
Why the Bad Rap?
Sadly, the pit bull has acquired a reputation as an unpredictable and dangerous menace. His intimidating appearance has made him attractive to people looking for a macho status symbol, and this popularity has encouraged unscrupulous breeders to produce puppies without maintaining the pit bull’s typical good nature with people. To make matters worse, irresponsible owners interested in presenting a tough image often encourage their pit bulls to behave aggressively. If a pit bull does bite, he’s far more likely to inflict serious injuries than most other breeds, simply because of his size and strength. A pit bull bite is also far more likely to draw media attention. Many dogs of other breeds bite people, but these incidents almost always go unreported. They’re just not exciting enough fodder for television and print.
Despite this bad rap, a well-bred, well-socialized and well-trained pit bull is one of the most delightful, intelligent and gentle dogs imaginable. It is truly a shame that the media continues to portray such a warped image of this beautiful, loyal and affectionate breed. Pit bulls once enjoyed a wonderful reputation. Some of the most famous dogs in American history were pit bulls. A pit bull named Stubby, a decorated hero during World War One, earned several medals and was even honored at the White House. During duty, he warned soldiers of gas attacks, found wounded men in need of help and listened for oncoming artillery rounds. Pit bulls have been featured in well-known advertising campaigns for companies such as Levis, Buster Brown Shoes and Wells Fargo. The image of a pit bull, which was considered a symbol of unflagging bravery and reliability, represented the United States on recruiting and propaganda posters during World War One. Many famous figures, including Helen Keller, President Theodore Roosevelt, General George Patton, President Woodrow Wilson, Fred Astaire and Humphrey Bogart, shared their lives and homes with pit bulls.
Modern pit bulls can still be ambassadors for their breed. Some are registered therapy dogs and spend time visiting hospitals and nursing homes. Some work in search-and-rescue. Tahoe, Cheyenne and Dakota, three search-and-rescue pit bulls from Sacramento, California, worked tirelessly at the World Trade Center during the aftermath of 9/11. Others, like Popsicle, an accomplished U.S. customs dog, work in narcotics and explosives detection. Still others serve as protection or sentry dogs for the police. The majority are cherished family members. Pit bulls become very attached to their people, and most love nothing better than cuddling on the couch or sleeping in bed with their pet parents (preferably under the covers)!