It is a complex problem - the fact is that the type of owner most likely to produce (deliberately or accidentally) aggressive responses in any type of dog are more likely to go for certain breeds - because of their reputation deserved or otherwise. This compounds the problem of putting dogs that have the probability of aggressive responses in the hands of people that are probably going to provoke an aggressive response.
I still believe over all owners are more of a problem than the actual dogs. While there are bad blood lines in some breeds and mixing breeds can make things worse these account for a very small number of animals - meanwhile bad owners get dogs without the problem bloodline to become problems - dogs that if in other hands would never have been a problem. I think it terribly short sighted of authorities to focus on breed and dog type - they would reduce aggression far more effectively if they focused on owner type.
