The vast majority of pit bulls will never become aggressive toward humans. That said, "Terrier" is in the name for a reason. These are large dogs with an instinct to bite, hold, shake, and do not want to let go. When bites happen to humans or other animals, they can be devastating. The problem with pitbull type dogs is not necessarily the frequency at which they bite, but the way that they bite.

Surely you can see the horrid conclusions this type of reasoning results in, just in general

I think I understand where you're going with this, but for the sake of clarity, can you elaborate?