In my neighborhood, the law requires that dog, and one other to be fenced, chained, or on a 6 foot or less CHAIN LEASH. In addition there is a MANDATORY insurance requirement of no less than $1000.00 (I think) per dog. Their jaws have much in common with alligators, for their closing strength is very high. Behavior IS a matter of conditioning, however, very few people ever train their dogs to be sweet, gentle, little lambs. Most are used for protection of people and property, and that is by it's very nature aggression. Rolling over for a tummy rub, just doesn't get the job done. I will, without question, shoot to kill any dog that threatens me or my family, Pitt-bulls get no second chances with me. I already lost one pet due to roaming dogs.
The only real difference between a good tracker and a bad tracker is observation. All the same data is present for both. The rest is understanding what you are seeing.