The pit bull statistic isn't that great. Ie if you have 100 pitbulls walk past you, there are 15 that are going to try to eat you? Though the temperment test isn't clear if they fail because they try to attack or fail because they try to run away.
And if a pit bull tries to eat you, it's going to do a lot more damage than a cairn terrier (which also has a crappy pass statistic).
However the pit bull statistic isn't significantly different to the labrador statistic at 90% ie if 100 labs walk past you, about 10 will try to eat you - which is about right, based on my face to face experience with Labradors.
So my point would be possibly the same as Aussiemyf in that dogs should be assessed on their individual merits not their breed. But it might be a sensible requirement that a stronger bigger breed be required to pass at a higher standard than a smaller breed that is less able to do damage if it attacks.
And I agree with the UK approach - that some *people* should be banned from owning dogs full stop. If this person owns a dog that gets out and attacks people, this person should be banned from owning a dog, looking after a dog or sharing a house with one.