Problem dogs, we've all met them. As a child a neighbour's Collie regularly chased me the length of the street, at the time it felt like I was running for my life. But now I know that the dog wasn't trying to eat me, it was herding me. It was following its natural instinct and doing the job it was bred to do.
We need penalties for those owners who allow their dogs to attack and kill other dogs, cats, and other animals. We need better controls on dog breeding, advertising and sales. Only when we insist on better behaviour from the person on the other end of the lead will we be able to address the dangerous owner problem.