There are more family dogs, such as Labradors, that bite people more than pit bulls do - however, because there is such a small number of pit bulls and such a large number of Labradors, it seems fairly concentrated down to the point it makes it out that pitbulls are the bad dog.
It's also very hard to identify Pit bulls because they aren't actually a real breed, they're just a cross, and a lot of people in court use that to their advantage.
They are bred for fighting and I do believe that is in their blood, however, it all traces back to ownership - anything the owner does will reflect in the dog's behaviour. I know from work experience the "big bad" dogs that people seem to be afraid of (such as staffies, rottweilers etc) are 100 times nicer than those wee rats of a dog (jack russells etc). It depends entirely on the owner, but it's not just pit bulls that are a banned breed.
Also, there needs to be tougher sentencing on the people who carry out the fighting. They walk free after forcefully pitting 2 dogs against each other to the death, whilst training them using live bait - what sort of message does that put out?