1. Pit bulls are specifically bred to NOT be aggressive to people. Fighting dogs are handled by their opponents' owners prior to fights to make sure there's no cheating going on. The dog attacks it's opponent's owner, it is put down, end of. It is aggression to other dogs (or bears or hogs, etc) that pit bulls are bred for.
Any pit bull that shows aggression to people is acting wildly out-of-character and should be euthanized immediately.
2. Dog bite statistics are notoriously inaccurate. Far more people are bitten by golden retrievers or German shepherds than by pit bulls. These incidents tend to not get reported, though. Pit bulls just wind up in the news more easily because they look mean. Statistics from England, where pit bulls were banned, do not indicate much, if any, reduction in dog attacks.
3. Pit bulls are a mish-mash of breeds that can look similar. An attack by a presa canario or American Bulldog, etc are often attributed to pit bulls.
4. Yes, a lot of people that cannot handle pit bulls own them. You cannot be a type-b person and get by with a pit bull. They should always be supervised around children and other dogs. Owners should be well-trained in how to break up fights before they escalate into death matches. Licensing standards need to be improved for this breed. And laws for dog fighting need to be relaxed in order to give police more lattitude to arrest the scumbags / idiots / milquetoasts that either use them for nefarious purposes or cannot handle them.
5. The dogs in this video should have been put down by the police officer then and there.
I've had several pitbulls in the past and each one of them was rather serene. But they were also well aware that if they did anything wrong, they would have to run far to be safe.
We're talking about 25-35 deaths in the US from dog attacks (not sure about ROW, but would assume consistent figures for given populations). There are far better uses for people's attention.
http://www.dogbitelaw.com/PAGES/danger.htm#statistics