When I work with clients who are having nipping issues, I find it is often the failure of the family to properly address this. Now, the puppy has been taught biting is acceptable and is well on the way to becoming a biting problem as an adult. Or, people mistakenly think that watchdog is analogous to vicious and intentionally train the dog that way. This is wrong thinking and often dangerous. Now, let us address breed identification.
Pit is often a catchall phrase used indiscriminately.
When I was starting out in dog training, I went to a seminar that addressed breed bans. Not one was. The dogs were all champions of record and the breeds included a Boxer, a Lab, a Bullmastiff and a couple others. The other point was than bans will only affect the responsible owners and drive those who have no business owning ANY living creature further underground. And if they run out of one breed, they will go for another.