The mouth-breathing semi literate thug with the neck-tattoos and the pitbull isn't an owner-occupier. The chances are he's housed in council or housing association rented accommodation. He has no right to keep a dog unless at the landlord's consent - or face eviction.
The answer to 'weapon dogs' isn't yet more unworkable legislation from the central State, it's for councils and social landlords to do their job.
I'm pretty sure that for the past ten years of living in private accommodation, none of my landlords have allowed any pets, not that I've had any urge to get one. I can barely afford to provide for myself and the missus, another mouth to feed with have to come later.
So likewise, if the state wishes to reduce the number of dangerous dogs then all they have to do is start saying "no pets allowed".
If its a penniless pensioner with a shih tzu for companionship, then the council can make them an exception.
But other than that, when the housing officer comes round, either the dog goes or the owners get evicted.