Look at your own argument though. You've had him for 8 years and not attack. There are many stories just like yours where people have raised a Pit Bull from a puppy and then it kills a child in the home. Again, the first sign of aggression ever was the killing of the child. The dog had lived in the home for many many years with no aggression until he killed the child. This Titusville attack, the child had lived with the dog for 4 years.
If the dog wasn't raised right, he wouldn't have waited 8 years to attack. He would have attacked much earlier.
I have a 13 year old dog and a 16 year old dog who recently died. Both have nipped me for no apparent reason. They are small dogs so a nip just draws some blood on a finger. These dogs have been with my wife and I since we were first married. They were are first children. They have been family members for longer than my children have been. They have always been well trained and treated, yet they nip. They nipped me doing things with them that I had done 1000's of times (playing, taking things away). Yet on 2 occasions for whatever reason they decided to bite. With a less aggressive breed this isn't a problem. With a pit bull it's like spinning the chamber on a gun and putting to your head. Like I said, (and look at the incident reports) they go for the throat and face, instinctively. Most predatory animals do.
The problem is that you don't even know what it is that is going to set them off. No amount of training or uber owner skills are going to help you. It might not even be something you did. It might be that there is a dog in heat 5 houses down the street and you aren't even aware.