There are professional people who can tell you about specific breeds and animals.  Pit Bulls are an aggressive breed.  I have been told that you need a pry stick to unhinge their jaw once it is clamped.  Which means that they can do a lot of damage.  Some dogs are from show lines, and some may be from fighting lines, but in any litter of pups, in any breed there is generally an alpha dog, and a most submissive one.  It is upsetting to hear people continually say that it is the way they are raised.  Of course that has something to do with it, but according to that theory, any dog could be a police dog or soldier.  That is simply not true in my opinion.  Dogs of any breed, just like horses, and people, are as different as night and day. It is not surprising that good, kind, dog owners get disappointed when their always sweet terrier acts aggressively unexpectedly.  Some types of dogs have very strong prey drives, and more than one dog may compete with each other.  This is not to say in my opinion that some dogs cannot be managed with careful handling, and an educated owner. The bottom line is that terriers are known as a more aggressive breed, and Pits were bred to fight initially, but some of them are fabulous. Why punish all at the expense of some bad ones that are out there. How many labs bites have been reported?  Find out! With labs being crossed or bred with no regard to temperment it may surprise us.