Not all owners of the Breeds of Dog in question are scrotes, or have these dogs as a status symbol "look at me I'm hard" thing.
I bought my Staffordshire bull Terrier from Pup 6yrs ago, purposely as a training partner, someone to motivate me in the morning and at night for long runs and I'd take him Cycling (yes he can cycle haha :P )
He has a set routine Tue-Thu-Sun where he goes on long walks, swimming in the lakes/rivers and as I type this he's fast asleep snoring his head off too tired to want to bite some kids head off as he is trained properly.
Food after exercise, he knows why he is exercising as he gets rewarded with food.
Dogs attack out of Fear. I purposely trained my Dog to not have this fear, which is why many dogs have attacked him and he's just brushed it off almost like he's just sparring.
Funny ain't it, the amount of Dogs that have attacked my dog, and they are usually the more "Pet" type breeds, the small Maltese, Pugs, Pomeranian types which Celebrities have made fashionable....
Because the owners have fear after seeing my Dog, their dogs detect this fear after the owners usually pick them up off the floor or go into anxiety/panic mode and before you know it their dogs are going sick and trying to attack my dog.
My Dog has yet to attack any other dog or human. it has however defended itself when all kinds of breeds have gone for it.
The problem with the Test/License system is many scrotes have their Dogs bred with illegal dogs...so they'll have a staffordshire bull terrier bred with an American Bull terrier (illegal)
And the Police will be none the wiser. they could have the license and pass the test, but they are walking the streets with a dog that's cross bred with an illegal breed.
My Staffie is full KC registered, has his breed history traced back over 100yrs and was bought from an home where the woman/Male lived with Children.
Sort out the money making scrotes who breed these dogs with no set standards, just breeding to make cash (dogs aren't socialised, just in cages) and you'll be a step closer to eliminating the vicious breeds that are bred with other breeds.
Don't buy your dogs from these people, buy dogs from loving homes.