The law should be such that if a dog harms someone such that they need hospital treatment, the owner faces the same criminal charge as if they had inflicted the injury (or worse) personally themselves.
If your dog were to kill someone, you face a charge of manslaughter.
I'm a dog owner and I agree with this too. When you get a pet, you have a responsibility, not only TO them but FOR them. Their behaviour is your responsibility.
As a dog owner I made a commitment to them to give them a loving home, a good life and teach them right from wrong. They're like toddlers. Not much capacity from higher reasoning but you can teach them basic manners and link words to actions.
Most dogs are trainable. There is no reason for not doing so, just laziness or ignorance, neither of which is an excuse when you own an animal capable of doing serious damage.