While I agree that dangerous dogs are the fault of the owner, rather than the breed, I think your article is rather simplistic.
Some breeds will always have greater potential to become dangerous than others.
Any dog, trained well, will be good, well behaved and unlikely to cause problems. I'm sure your staffie falls into this category and I've met a fair few myself.
However, not everyone will train their dogs well - and this is when the breed begins to matter. Most dogs that haven't been trained will become unpredictable and some become aggressive. The level of agression is almost predisposed by breed. Now once you have an agressive, unpredictable dog, the next factor that will define how dangerous the dog is would be their size and strength.
Terriers, by their very nature were bred for killing pests or fighting. This means that their instincts are quite different to some of the other common breed families and makes them more susceptible to aggression if they haven't been well trained. In your smaller terriers: jack russells, yorkshires, etc. as noted above, the owner is easily able to restrain them when they're aggressive. For larger breeds, such as staffordshires, pitbull, bull, etc. the dogs are considerable stronger and are capable of terrible injuries.
This is why staffordshires get the bad rep and at the risk of winding a few people up, it is justified, though no fault of the dog itself.
Offer me the choice between rehoming a poorly treated labrador and a poorly treated staffie and I know which one I would consider the safest bet.